Well, this is actually more a bug fix than a new feature but this sounds much better 
.
Because of how Uptime Robot was handling/filtering URLs, monitors with querystrings couldn't be added. And, it is fixed now.
So, it is possible to monitor a URL like http://ww.mydomain.com/index.php?item=1&price=15.
Also, in some cases, multiple notifications were being sent for the same alert, which is also fixed now. Simply, one notification per one alert contact.
Hopefully, more features to come this week. Keep an eye on!