Monitoring Network Connections

I have a system which connects to several different system in a variety of ways... ADO connections, file sharing, etc.  This system performs several important tasks.  Unfortunately it occassionally loses connectivity in one way or another, so the tasks that it is trying to perform fail.  I cannot change most of these tasks, so what I would like to do is monitor connections and send a message (email, pager, cell text message) if there is a loss.  I have written some small jobs that would provide this functionality in the past, but I imagine there must be a tool created which provides this type of functionality.  Is anyone familiar with a package that provides this?

And, of course, cost is a factor!

Thanks In Advance,

Michael