i use xAP Ping ( http://www.mi4.biz
) to monitor my web servers, my internet connection, various apps (slimserver, medianet, tversity), networked devices (networked amp is powered on or off, etc)
it can monitor an app or device via http, tcp or ping and it can also monitor drive space memory. it can also do an odbc database check (whatever that is
and of course, all the results can be acted upon by scripts.