I run a couple of servers on my home network, so I have my DSL router set up to forward several ports - port 80 for example, for my www server.
I use a free service called Uptime Robot (uptimerobot.com) to monitor each of these ports. It tries to contact each of my servers every 5 minutes, and notifies me via email, text message, app pop-up on my iPad and Android phone if one (or more) goes down.

I imagine that it could be configured to work with a dynamic ip system without too much work