A webcam and a few scripts will do (Score 2, Informative)

I use a dlink DCS-1000W in a weatherproof enclosure mounted on the outside of my house. I have a cron script that grabs the image off of it every 30 seconds and uploads it to my linux box at the house. I have a web page on my server at work that dynamically grabs that picture each time the page is loaded. I can view that web page on my blackberry at any time to see what is going on at the house. My application is more security monitoring than baby watching, but the technique is the same.

The next improvement is to use motion (available on sourceforge) to detect when something is happening, take a few pictures, and mail them to me.