1. Click the gear icon at the top of any page and select Settings from the drop-down menu
2. Click the Mobile Setup tab
3. Select your country from the Country drop-down menu
4. Enter your phone number in the Phone number field
5. Select your carrier from the drop-down menu, if applicable. If you see the link See Help Center for supported providers, please check if your provider is supported before requesting your verification code.
6. If your carrier is supported, click the Send Verification Code button, and you’ll get a text message on your phone
7. Once you receive this message, enter the code you received in the Verification code field and click the Finish setup button
8. Click Save

/**   Website Monitor 4.0 by Digital Inspiration    **/
/**   ==========================================    **/

/**   Published by Amit Agarwal on 02/14/2013       **/
/**   Last updated by @labnol on 10/15/2013         **/

/**   Details at http://labnol.org/?p=21060         **/

/**   Support: [email protected]   twitter: @labnol   **/


function onOpen() {  
  
  var sheet = SpreadsheetApp.getActiveSpreadsheet();
  
  var menu = [ 
    {name: "Step 1: Initialize", functionName: "init"},
    {name: "Step 2: Start ", functionName: "init"},
    {name: "Uninstall (Stop)", functionName: "removeJobs"}
  ];  
  
  sheet.addMenu("Website Monitor", menu);    
}

function init() {    
  
  removeJobs(true);
  
  var sheet = SpreadsheetApp.getActiveSpreadsheet();
  
  var urls = sheet.getSheets()[0]
  .getRange("B2").getValue();
  
  urls = urls.replace(/s/g, "").split(",");
  
  var time = (new Date()).getTime();
  
  var db = ScriptDb.getMyDb();
  
  for (i=0; i<urls.length; i++) {
    db.save({url: urls[i], status:200});    
  }   
  
  // Setup trigger that runs every 5 minutes
  
  ScriptApp.newTrigger("init")
  .forSpreadsheet(sheet)
  .onEdit()
  .create();
  
  ScriptApp.newTrigger("websiteMonitor")
  .timeBased()
  .everyMinutes(1)
  .create();
  
  sheet.toast("Google Docs will now monitor your website(s). "
              + "You can exit this sheet!", "Initialized", -1);
}

function websiteMonitor() {  
  
  var db = ScriptDb.getMyDb();  
  var results = db.query({});
  
  while (results.hasNext()) {
    
    var item = results.next();    
    var code = -1;
    
    try {    
      var response = UrlFetchApp.fetch(item.url);
      code = response.getResponseCode();    
    } catch(error) {}
    
    item.status = alertUser(item, code);     
    db.save(item);
    
  }
  
}

function alertUser(item, code) {
  
  var status = item.status;
  
  // Status unchanged
  if (code === status) {
    return code;
  }
  
  // Site was up previously but is now down
  if ((code === -1) && (status === 200)) {
    // Run another check after 1 minutes to prevent false positives
    quickCheck();
    return -2;
  }
  
  // Site was down previously but up on second check
  if ((code === 200) && (status === -2)) {
    return code;
  }
  
  // Site was down previously and is down again
  if ((code === -1) && (status === -2)) {
    quickCheck();
    logMessage(item.url, "Down");
    return code;
  }
  
  // Site was down previously but up again
  if ((code === 200) && (status === -1)) {
    logMessage(item.url, "Up");
    return code;
  }
  
  return 200;
}


function logMessage(url, message) {
  
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  
  var row   = sheet.getLastRow() + 1;    
  var time  = new Date();  
  
  sheet.getRange(row,1).setValue(time);
  sheet.getRange(row,2).setValue(message + " : " + url);
  
  var alert = "Site " + url + " is " + message.toLowerCase();
  
  MailApp.sendEmail(sheet.getRange("B3").getValue(), "Site " + message, alert);  
  
  if (sheet.getRange("B4").getValue().toLowerCase() == "yes") {
    time = new Date(time.getTime() + 15000);
    CalendarApp.createEvent(alert, time, time).addSmsReminder(0); 
  }
  
  return;
}

function secondCheck() {
  
  var triggers = ScriptApp.getProjectTriggers();
  for (var i=0; i<triggers.length; i++) {
    if (triggers[i].getHandlerFunction() == "secondCheck") {
      ScriptApp.deleteTrigger(triggers[i]);
    }
  }
  
  websiteMonitor();
  
}

function quickCheck() {
  ScriptApp.newTrigger("secondCheck").timeBased().after(120000).create();
  return;
}

function removeJobs(quiet) {    
  
  // Clean the database
  
  var db = ScriptDb.getMyDb();
  
  while (true) {
    var result = db.query({}); 
    if (result.getSize() == 0) {
      break;
    }
    while (result.hasNext()) {
      db.remove(result.next());
    }
  }
  
  // Delete all Script Triggers
  
  var triggers = ScriptApp.getScriptTriggers();
  
  for (i=0; i<triggers.length; i++) {
    ScriptApp.deleteTrigger(triggers[i]);
  }
  
  
  // Inform the user, default is "YES"
  
  if (! quiet) {
    
    var sheet = SpreadsheetApp.getActiveSpreadsheet();
    
    sheet.toast("The program has stopped. You can choose Start under Website Monitor "
                + "menu anytime later to resume website monitoring!", "Uninstalled", -1);
    
  }    
}

// Written by Amit Agarwal [email protected]
// Twitter: @labnol