It's obviously going to happen: there's a lot of research going on (and that's only what you can find on the Web.) The military would certainly find use for something like that. So would the police: want to see what the bad guys are doing before they see you? Send a few of these things in first. Not a new idea at all: plenty of precedent in science-fiction. It's just that we're finally acquiring the technical capability to pull it off.
Tie them in with those proposed mobile mesh-networked mines I was reading about recently. The flying probes could tell the mines where the intruders are.
The only issue I can see is going to be an adequate power source. Lithium-ion batteries aren't going to cut it. Fuel-cells, maybe.