You could try something like the Zigview. I don't know how well they work or if they will work on your particular camera, but they have a motion sensor built into them.

http://www.argraph.com/Zigview/page1/Zigview_page1.htm

There are other motion sensor triggers on the market, but they aren't cheap.

A much more inexpensive option would be a trail camera that you can pick up at just about any decent department or sporting good store.

I had a 35mm trail camera given to me a few months ago. My plan is to some day try to take it apart and build a motion trigger I can use on a DSLR but who knows if I will ever get to it...