I just reviewed a couple of these from Day 6 Outdoor called PlotWatchers and I was amazed out how well they work. I wanted to know if anyone else had tried them in the field? They are great for scouting. You can see my video clips at: http://www.toxiegivens.com/?p=483
Reconyx cameras have this feature built into them. I haven't used it yet though, Its a great idea I just haven't placed the camera were it warrants using it yet. I do plan too soon though.