[JavaBrewer]

Yes they can install wireless door/window sensors. Quick and easy for them. IMO a pain for the homeowner - the batteries last a couple years and the sensors mount in highly visible manner. If you don't need 24hr automatic response then a DIY kit would work just as well as anything from the likes of ADT.

Or you could just buy some signs & window stickers and call it a day. IMO that alone will deter 95% of the would be thieves.