YES (to both).
there are bug detectors that will tell you if (and where) a wireless electronic device is active in the room, including microphones, cameras, and metal detactors.
...There are also scramblers available that will distort (scramble-up) the signals that these wireless devices are sending to their receivers...as well as decoders that will allow you to capture that signal for yourself, if desired.
*Those Hollywood spy movies, like most rumors, are based on a little bit of fact.
Not intending to further your insecurity, but it's fairly common today to find hidden security cameras in smoke detectors, desk and wall clocks, exit signs, 2-way mirrors, and many semi-permanent mounts that allows access to the dime-sized lens of the popular CCD cameras.
While most of these uses are legitimate security measures (despite the fact that a few retailers have been sued for the cameras in dressing rooms, monitored by male security staff), there are also a few deviate uses for the tiny cameras that you are obviously aware of.
Prevention is pretty expensive, and the best simple defense is to be aware of the possible placements of an un-authorized device.
Small holes in the ceiling tiles are a possibility of course, just as any wall-mounted device (air freshener system, napkin machine, hand dryer...especially the toilet tank) can hide a tiny camera.
Just as a security expert would, you first need to think like a pervert...where would you hide a device (about the size of a quarter) to get the best pictures?
Don't allow paranoia to take over, but being aware is usually the best defense...the most common victims are totally unaware that this faction of our society even exists.