This device can be used for many things beyond mouse cages.  My wife and I have two parakeets, so I zip-tied a PIR device near their feeder and found that they eat almost exclusively during the day.  (I already kind of knew that but it's neat to see the data!)

Update 10/09/18:

3 weeks of data on one charge!  The variance in daily feeding early on was the result of us putting a different food source (a "treat stick") in the cage on 9/23.  Still, there is a lot of daily variance in activity near the feeder, maybe some days they're hungrier than others?