Google Apps Scriptを使って簡易APIをサクッと作る ref: http://qiita.com/edo_m18/items/0519d241ac7683815a53

GAS.js

function doGet(e) {
  return makeContent(makeResponse(e, "GET"));
}
function doPost(e) {
  return makeContent ( makeResponse(e,"POST"));
}

function checkId(id) {
  var ss = SpreadsheetApp.openById('0ArR-uXirGVyWdFJ1WFZyclpMRzA5dmhnaVMxa29zNlE');
  var sheet = ss.getSheetByName('sheet1');
  var range  = sheet.getRange(1, 1, sheet.getLastRow(), 1);
  var values = range.getValues();

  var result = false;

  values.forEach(function (row) {
    row.forEach(function (val) {
      if (result) {
        return;
      }

      if (val === id) {
        result = true;
        return;
      }
    });
  });

  return result;
}

function test() {
  Logger.log(checkId('abca'));
}

function makeResponse (e, type) {

  var valid = checkId(e.parameter.presentCode);
  e.parameter.valid = valid;

  var s  = JSON.stringify({type: type, params: e});

  if (!e.parameter.callback) {
      return {mime:ContentService.MimeType.JSON,  content: s};
  }
  else {
    return {mime: ContentService.MimeType.JAVASCRIPT, content: e.parameter.callback + "(" + s + ");" };
  }
}
function makeContent( content) {
  return ContentService.createTextOutput(content.content).setMimeType(content.mime);
}