Our 2nd year BSc Software Development for Animation, Games and Effects students have built a portal turret using a Raspberry Pi, OpenCV and a web cam to track and fire on people in the room. It uses 3 arduinos to control the servos and nerf guns. They are currently writing up a making of but though I would post the initial videos first.
This has been developed as part of their Software Engineering module where they had to design, cost and develop a "product" from scratch determining what software / hardware to use. For more details on the course have a look here.
http://courses.bournemouth.ac.uk/course ... hons/1082/