I signed up with ThrustVPS on Jul 27, 2010. Sounded like a good company although I read a lot of bad review about Rus Foster who is now leading this new venture previously known as DamnVPS. There were lots of issues in the start and not to mention so many down times that went unaccounted for.
I have been experimenting with NAGIOS3 on Ubuntu (I will write a how-to-install on NAGIOS later) and it has served me very good in monitoring my 7 VPS from different providers in different part of the world. I have already recorded 3 hours of downtime from ThrustVPS which is a great deal for me. I now know which VPS has the best time and which ones have hiccups (e.g. my 2Host VPS gave me two unreachable notifications but the VPS was running and still reports the uptime as 4 days).
Since I use twitter more, even when Im on the road, notifications via email is a bit slow for me. Luckily I found a great tutorial online to do that.