I use cgminer on all my machines and hooked into the api to poll for current statistics. From there I threw together a quick Android app which displays all the machines and their current temperature, fan speed, hash rate, etc. on my phone. As you can see each machine can be expanded out to view the individual GPUs, FPGAs, and (hopefully soon) ASICs connected. The Android device must be on the same wifi network as the miners, but I've been tossing around the idea of putting together a web service to make the data available with just an internet connection. It doesn't make configuration changes to the miners, but at least I get notified immediately.
Here is a sample screenshot with a few test machines. I was in the middle of simulating several different conditions when the screenshot was taken.
https://s3.amazonaws.com/lwcoder-images/bitcoin-assistant/screenshot-2012-07-04-171421.png