I almost missed this excellent post on system monitoring by (I think) Yanick Champoux. It’s a clever idea. The monitor has a bunch of TAP1 tests that check various parts of the system – e.g. whether diskspace on a particular partition has breached a certain threshold.
The tests are all run with Smolder, "a web-based continuous integration smoke server". This means that the results can be made available via email, RSS or Smolder’s web interface. Very neat.