I created a Windows Phone 7 app that lets you monitor your webservers. It does a request to all the servers and determines if they are up and running.
You would expect PUSH notifications in this kind of application. However, that's not implemented right now. You'll need an internet connection on your phone, because the phone does the webrequests to the servers.
Results are presented in a list.
The application can be found in the Tools category of the Zune Store.
In Trial mode, you can add one server.
The Full Version lets you add unlimited servers.