.launch_and_focus.slate.js

// アプリにフォーカスする。アプリが起動していなければ起動する。
var launch_and_focus = function(app_name) {
    var launch = function(app_names, win) {
        if( _.any(app_names, function(name){ return name == app_name; }) ) {
            return;
        }

        win.doOperation(
            slate.operation('shell', {
                'command' : '/usr/bin/open -a ' + app_name,
                'waitForExit' : true
            })
        );
    };

    return function(win){
        var app_names = [];
        slate.eachApp(function(app_obj){ app_names.push(app_obj.name()); });
        launch(app_names, win);
        win.doOperation( slate.operation('focus', {'app' : app_name}) );
    };
};

var key_binds = {};
key_binds['1:alt'] = launch_and_focus('Google Chrome');
key_binds['2:alt'] = launch_and_focus('iTerm');
key_binds['3:alt'] = launch_and_focus('Emacs');
key_binds['4:alt'] = launch_and_focus('Skype');
key_binds['5:alt'] = launch_and_focus('Things');
slate.bindAll(key_binds);

.switch_app.slate.js

// oo というアプリにフォーカスしてる時、次は xx というアプリにフォーカスする
slate.bind('j:alt', function(win) {
    var focus_apps = {
        'iTerm' : 'Emacs',
        'Emacs' : 'iTerm'
    };

    var app_name = win.app().name();

    if (!(app_name in focus_apps)) return;

    win.doOperation(
        slate.operation('focus', {'app' : focus_apps[app_name]})
    );
});