I thought about the internet camera as well, but I realized that means you need to have
1. Electricity turned on
2. Internet (preferably wireless) at your parent's house.
I have a few of those "DLink" cameras at my house and it really is awesome for $99. You can have it send you an email with a still picture every time the motion detector is set off. It works great if you have "Push" email set up on your phone.
dlink 942 - Google Search