I had to solve this problem once with zero budget. It was the single most clever thing I've ever done. I'm immensely proud of this.
I had a problem with my server room where, sometimes after a power outage, the HVAC would stop working (it wouldn't automatically start up again correctly after the power outage), and I'd come back after a long weekend to a cooking server room. I tried to get them to fix the HVAC and after about 20 visits they still couldn't fix it. My only solution was to reset the HVAC by hand when it happened. So I needed to know, via email and/or SMS, any time the server room busted a certain temperature threshold so I could go into the office and reset the HVAC.
I had a similar problem - after a power failure, the building's chillers (which we tied into) wouldn't reset, and our HVAC would overload and go offline. We had to do manual reset. Without AC, it took about 90 minutes for the server room to get so toasty as to wipe our firewall. Just a quick reload from backup, but it sucked on weekends.
I was no where as close to as clever as you, though: I used an APC sensor and device (it seems to have been replaced by a much more expensive "NetBotz" get-up) which sent a half dozen emails to personal email accounts and cell phones in the hope
someone was available to drop everything and rush in.
If we got there in time, we could open a couple doors, set up our fans, and keep it barely cool enough indefinitely. Fortunately it only happened about once a quarter.
-jk