I had the same problem with mine, it turned out to be a wireless router that also broadcast on the same channel as the controllers. Started happening the same day I picked up a wireless N linksys router. I just got into the routers settings and changed it to from channel 1 to channel 5, seemed to fix it. There is no sensor, the controllers have an RF radio in them which communicates with the consoles RF radio.

Edit: saw that ps3 comment... have fun once the battery in the controller goes bad. A friend of mine had to replace both his controllers after about 6 months because they wouldn't hold a charger longer than about an hour, and you cant replace the batteries.