Motion (or Infrared?) detectors for lights or electronics?

[gaikokujinkyofusho@xxxxxxxxx]

Hi, I can't imagine this hasn't been asked before but I couldn't find
any other similar postings. I am trying to find some sort of gadgets
that that one can plug electronics (or screw in between bulbs and
sockets) into that will turn on when someone enters a room and stay on
until they leave the room (might not work so great for a bedroom but
seems useful for other rooms).

Does anyone out there know of such gadgets and where I can find them?
Any help would really be appreciated!

Cheers

-Gaiko