Probably the type thing the OP is making.
http://www.youtube.com/results?search_query=sentry+gun&oq=sentery&gs_l=youtube.1.6.0i10l3j0j0i10l6.2738.8199.0.12868.7.6.0.0.0.0.252.1225.0j3j3.6.0...0.0...1ac.1.YUY8iu8zMnU
