Andy writes:

Sure. They cost about 10 bucks at Walmart and are normally
used for driveway and outside monitoring. Just buy one and
hook it to an electrical cord and place it somewhere to experiment
on the coverage.....
The biggest drawback I can see is that they probably won't fit
in with your decor, but you can hide it behind something that is
transparent to infrared, or in the foliage of a fake plant, or
something.... The sensors are the same as the expensive ones
that is used in stores, except the Walmart versions are mass
produced which gets the price really low......
Get one and try it out. Use it to turn on a floor lamp or
something and let your imagination run with it.....
However, if you fall asleep on the couch at 11pm, expect to
wake up with the lights out. Just wave your arms and they will
come on. If you toss and turn in your sleep, the damn thing
will go on and off and you probably will unplug it.... (grin)....

Andy