app.js

/*jslint maxerr:1000 */

Ti.API.info("Require the CommonJS module");
var guid = require("guidtools");

Ti.API.info("Requesting a new guid");
Ti.API.info("GUID value = " + guid.generate());

guidtools.js

/*jslint maxerr:1000 */
exports.generate = function(){
	var guid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
	    var r = Math.random()*16|0, v = c == 'x' ? r : (r&0x3|0x8);
	     return v.toString(16);
	});		
	return guid;
};

Sample from broofa on on stackoverflow.com at the below link

http://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript