This gist contains a homebridge.js accessory that tries to mimic the elgato eve weather and it's history.

ElgatoEve.js

var Service = require("HAP-NodeJS").Service;
var Characteristic = require("HAP-NodeJS").Characteristic;
var request = require("request");
var inherits = require('util').inherits;
var debug = require('debug')('Eve');

var hexToBase64 = function(val) {
    return new Buffer((''+val).replace(/[^0-9A-F]/ig, ''), 'hex').toString('base64');
}, base64ToHex = function(val) {
    if(!val) return val;
    return new Buffer(val, 'base64').toString('hex');
}, swap16 = function (val) {
    return ((val & 0xFF) << 8)
           | ((val >> 8) & 0xFF);
}, hexToHPA = function(val) {
    return parseInt(swap16(val), 10);
}, hPAtoHex = function(val) {
    return swap16(Math.round(val)).toString(16);
}, numToHex = function(val, len) {
    var s = Number(val).toString(16);
    if(s.length % 2 != 0) {
        s = '0' + s;
    }
    if(len) {
        return ('0000000000000' + s).slice(-1 * len);
    }
    return s;
}

module.exports = {
    accessory: EveAccessory
}

function EveAccessory(log, config) {
    this.log = log;
}

function EveLogEntry(type, id, timestamp, sensorDatapoints) {
    this.type = type;
    this.id = id;
    this.timestamp = timestamp;
    if(type == 0x10) {
        this.sensorDatapoints = sensorDatapoints;
    } else {

    }
}

EveLogEntry.prototype.toHex = function() {
    var bytes = [this.type, this.id, 0x00, 0x00, 0x00, numToHex(parseInt(hPAtoHex(this.timestamp), 16), 4), 0x00, 0x00 ];

    if(this.type == 0x10) {
        bytes.push((this.sensorDatapoints.length * 2) + 1);
        bytes.push.apply(bytes, this.sensorDatapoints.map(function(s) {
            return hPAtoHex(s);
        }));
    }
    var bytesAsStrings = bytes.map(function(s) { return typeof s === 'string' ? s :numToHex(s); });

    // console.log(bytes, bytesAsStrings)
    return new Buffer(bytesAsStrings.join(''), 'hex').toString('hex');
}
var _eve = {
    EveService1: [
        {
            uuid: 'E863F10F-079E-48FF-8F27-9C2605A29F52',
            desc: 'Air Pressure Sensor',
            perms: [Characteristic.Perms.READ],
            format: Characteristic.Formats.DATA,
            value: hexToBase64(hPAtoHex(1234))
        },
        {
            /*
                Some kind of internal temp sensor? Returns 18.7 which is eq to first saved temp
                Temp low maybe?
             */
            uuid: 'E863F111-079E-48FF-8F27-9C2605A29F52',
            desc: '',
            perms: [Characteristic.Perms.READ],
            format: Characteristic.Formats.DATA,
            value: hexToBase64('4e07')
        },
        {
            uuid: 'E863F112-079E-48FF-8F27-9C2605A29F52',
            desc: '',
            perms: [Characteristic.Perms.READ, Characteristic.Perms.WRITE],
            format: Characteristic.Formats.DATA,
            value: hexToBase64('00000000')
        },
        {
            uuid: 'E863F11B-079E-48FF-8F27-9C2605A29F52',
            desc: '',
            perms: [Characteristic.Perms.READ],
            format: Characteristic.Formats.DATA,
            value: hexToBase64('64')
        },
        {
            uuid: 'E863F11E-079E-48FF-8F27-9C2605A29F52',
            desc: '',
            perms: [Characteristic.Perms.READ, Characteristic.Perms.WRITE],
            format: Characteristic.Formats.DATA,
            value: hexToBase64('01be00be 00f44fb8 0a000000')
        },
        {
            /*
                Some kind of internal temp sensor? Returns 21.01 which is well in range of temps
                Temp max maybe?
             */
            uuid: 'E863F124-079E-48FF-8F27-9C2605A29F52',
            desc: '',
            perms: [Characteristic.Perms.READ],
            format: Characteristic.Formats.DATA,
            value: hexToBase64('3508')
        },
        {
            /*
                Some kind of internal hum sensor? Returns 65.32 which is well in range of hum
             */
            uuid: 'E863F12A-079E-48FF-8F27-9C2605A29F52',
            desc: '',
            perms: [Characteristic.Perms.READ],
            format: Characteristic.Formats.DATA,
            value: hexToBase64('8419')
        },
        {
            /*
                Some kind of internal hum sensor? Returns 65.32 which is well in range of hum
             */
            uuid: 'E863F12B-079E-48FF-8F27-9C2605A29F52',
            desc: '',
            perms: [Characteristic.Perms.READ],
            format: Characteristic.Formats.DATA,
            value: hexToBase64('8419')
        }
    ],
    EveService2: [
        {
            uuid: 'E863F116-079E-48FF-8F27-9C2605A29F52',
            desc: 'Read Trunk 1',
            perms: [Characteristic.Perms.READ],
            format: Characteristic.Formats.DATA,
            value: hexToBase64('01010000 FF000000 3C0F0000 03010202 0203021D 00F50F00 00000000 000000')
        },
        {
            uuid: 'E863F117-079E-48FF-8F27-9C2605A29F52',
            desc: 'Read Trunk 2',
            perms: [Characteristic.Perms.READ, Characteristic.Perms.WRITE],
            format: Characteristic.Formats.DATA,
            value: hexToBase64(
                '1500 0000  0000 0000  0080 0000  0000 0000  0000 0000  00' +
                new EveLogEntry(0x10, 1, 0, [1870, 7214, 9900]).toHex()
              + new EveLogEntry(0x10, 2, 600, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 3, 1200, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 4, 1800, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 5, 2400, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 6, 3000, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 7, 3600, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 8, 3601, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 9, 3602, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 10, 3603, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 11, 3604, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 12, 3605, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 13, 3606, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 14, 3607, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 15, 3608, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 16, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 17, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 18, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 19, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 20, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 21, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 22, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 23, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 24, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 25, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 26, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 27, 3609, [1870, 7214, 1234]).toHex()
              + new EveLogEntry(0x10, 28, 3609, [1870, 7214, 1234]).toHex()
                // new EveLogEntry(0x10, 3, 1800, [1870, 7214, 9900]).toHex() +
                // new EveLogEntry(0x10, 4, 2400, [1870, 7214, 9900]).toHex() +
                // new EveLogEntry(0x10, 5, 3000, [1870, 7214, 9900]).toHex() +
                // new EveLogEntry(0x10, 6, 3600, [1870, 7214, 9900]).toHex() +
                // new EveLogEntry(0x10, 7, 4200, [1870, 7214, 9900]).toHex()
                // '1001 0000  0001 0000  0007 4e07  2e1c ac26' +
                // '1502 0000  00c8 0000  0081 3ce1  c21b 0000  0000 0000  00' +
                // '1003 0000  0059 0200  0007 6507  b919 a226' +
                // '1004 0000  00b2 0400  0007 e807  671d ac26' +
                // '1005 0000  0009 0700  0007 E807  671D 3930'
            )
        },
        {
            uuid: 'E863F11C-079E-48FF-8F27-9C2605A29F52',
            desc: 'Write Trunk 1',
            perms: [Characteristic.Perms.WRITE],
            format: Characteristic.Formats.DATA,
            value: null
        },
        {
            uuid: 'E863F121-079E-48FF-8F27-9C2605A29F52',
            desc: 'Write Trunk 2',
            perms: [Characteristic.Perms.WRITE],
            format: Characteristic.Formats.DATA,
            value: null
        },
    ]
}

var Eve = {},
    makeCharacteristicFromEveDesc = function(s) {
    var id = s.uuid.split('-')[0];
    Eve[id] = function() {
        var name = (s.desc && (id + ': ' + s.desc)) || id;
        Characteristic.call(this, name, s.uuid);
        this.setProps({
            format: s.format,
            perms: s.perms
        });
        this.value = s.value;
        var self = this;
        this.on('get', function(cb) {
            debug('[%s] was read', name, base64ToHex(self.value));
            cb(null, self.value);
        });
        this.on('set', function(val, cb) {
            debug('[%s] was written: %s', name, base64ToHex(val));
            cb(null, val);
        });
    };
    inherits(Eve[id], Characteristic);
};

_eve.EveService1.forEach(function(s) {
    return makeCharacteristicFromEveDesc(s);
});
_eve.EveService2.forEach(function(s) {
    return makeCharacteristicFromEveDesc(s);
});

function EveService1(displayName, subtype) {
    Service.call(this, displayName, 'E863F001-079E-48FF-8F27-9C2605A29F52', subtype);

    // Required Characteristics
    this.addCharacteristic(Characteristic.CurrentTemperature);
    this.addCharacteristic(Characteristic.CurrentRelativeHumidity);

    this.addCharacteristic(Eve.E863F11E);
    this.addCharacteristic(Eve.E863F10F);
    // this.addCharacteristic(Eve.E863F111);
    this.addCharacteristic(Eve.E863F112);
    this.addCharacteristic(Eve.E863F11B);
    // this.addCharacteristic(Eve.E863F124);
    // this.addCharacteristic(Eve.E863F12A);
    // this.addCharacteristic(Eve.E863F12B);
}
inherits(EveService1, Service);

function EveService2(displayName, subtype) {
    Service.call(this, displayName, 'E863F007-079E-48FF-8F27-9C2605A29F52', subtype);

    this.addCharacteristic(Eve.E863F116);
    this.addCharacteristic(Eve.E863F117);
    this.addCharacteristic(Eve.E863F11C);
    this.addCharacteristic(Eve.E863F121);
}
inherits(EveService2, Service);

EveAccessory.prototype = {
    identify: function(callback) {
        this.log("Identify requested!");
        callback(); // success
    },

    getServices: function() {

        // you can OPTIONALLY create an information service if you wish to override
        // the default values for things like serial number, model, etc.
        this.informationService = new Service.AccessoryInformation();

        this.informationService
          .setCharacteristic(Characteristic.Manufacturer, "Fakegato")
          .setCharacteristic(Characteristic.Model, "Eve Weather")

        this.service1 = new EveService1();
        this.service2 = new EveService2();
        return [this.informationService, this.service1, this.service2];
    }
};

@0ff
Hi, I'm experimenting a bit starting from your gist and the one from @gomfunkel. If you want you may have a look at my recent findings here https://gist.github.com/simont77/3f4d4330fa55b83f8ca96388d9004e7d. I don't know if you already discovered all of them, maybe we can join our efforts to close the ring.