Wireless IP cams are suuper cheap nowadays.
I have a few of these:
D-Link Products - DCS-932L - mydlink-enabled Wireless N Day/Night Home Network Camera
$99 each, $79 without the night vision.
You can set it up in your home and have it sync to your wireless. There's night vision and a motion detector; you can have the camera send you an email with a picture every time the motion detector is set off.
There's also an phone app where you can log on and watch live video of each cam from your phone, or you can log on from a computer if you like.
It's fun, but it's definitely only an add-on to an actual security system.