Looks useful. I've got a long-poll based monitor part written that I must get into a sensible state and chukc on github at some point. I was intending for it to monitor a few bits of mine in a semi distributed manner (each f my little bits of the net monitoring each other. The long-poll would mean I could "tick" every tens seconds (or even every second, though 10 was the plan) using very little bandwidth (it wouldn't have to be polling a web server either, but in all my cases it would be with the web server doing other local checks (Is the DB up?, Can I login?, No new errors in the critical-stuff log?, ...).

I might have to give your service a look until I finish my little toy, if I ever do.