Meet the RaspiTrap: a smart mouse trap that lets you know when you have caught a mouse. It does not harm the mouse but provides you with photo, video, and an e-mail when you have caught a mouse. The developer built an infrared barrier to detect when a mouse is inside. The device relies on a Raspberry Pi computer to alert you.
You will need to know a bit about Python to try this project. More information is available on Instructables.