Seems to work fine, but I got this when I added one of my sites:
2012-11-30 03:10:25 OK: Site added: http://example.com (is up).
2012-11-30 03:10:25 Warning: Site http://example.com is down.
I.e., it thought it was down, and notified me accordingly, but then shortly afterward it recognized it as up (which it was the entire time).I like the design :) clean and simple.
Just tried this out. Very simple and friendly sign up and setup. Looks great so far and seems to serve its purpose well. I will mention though that it felt odd having a link in the main navigation (Malware Scan) take me to a different website. Having not been familiar with Sucuri to begin with, I wasn't sure if it was an advertisement and how it related to UpMonkey. Thanks very much!