jimr451 - 6:50 pm on May 7, 2013 (gmt 0)
I've used alertra.com in the past. Though it's a hosted service you pay for monthly. If you host the solution locally, it won't be a good test, since if your external network goes down, the internal test will still work. If that isn't an issue, then I guess something local would be ok, but I don't know one offhand.