Try this post from Beelce on power strip hack for motion sensors like the one you saw 4 sale;
Motion Sensor / Power Strip .. Hack - HauntForum.com
Pick up a power strip for $6.00 ( make sure it has screw not the snap together cases,they break & are hard to deal with )
The motion sensors are lik $20, although to get a short time you need to set it on test for 5 sec on, shortest time
i buy the auto motion light switches ( cheapest at lowes over HD for $16 ), they have a 4 sec to 15+ min on feature that is adjustable
& a senor that is adjustable for sensitivity of motion sensor. I find these to be the best buy & with most timing options for the price !
here is a couple other sites to fest your imagination to build !!
HauntProject.com - Your visual source for Haunting How-To's
Monster Page of Halloween Project Links
you should find anything your twisted lil heart desires to build !!