I posted last summer how a good trail camera can provide important information in the war against deer... like where they enter your garden from and at what time. Buying a motion activated trail camera would be the easy way to get started collecting deer data, but not nearly as much fun as building one from scratch. LuridScience.com has an excellent step by step guide to hacking a motion sensor to work with a regular digital camera. I know it's a complex approach, but sometimes the road less traveled is where you learn some of the best hacking skills. The main reason I wanted to mention this was to provide help for those who might be trying to build a motion activated deer deterrent that makes use of digital coyote sounds.