Ask HN: how to develop a status page for a Rails app?

Hi everyone,

I have a huge Rails app with many usage points: web interface, 2 APIs, etc. and I want to show a status page for this app, decoupled from the app itself, of course, like GitHub, Bitbucket, Basecamp and so many others have.

How do you make this service know that the main services are running? How do they communicate? If the main service is on Rails, what do you use to develop the monitoring/status website?