The author of Crptonomicon, in one of his earlier books
I think it was "White Out"?
Had a character that was a supersonic cyberdog that had a thermal nuclear battery and a radar that let it see inside of people's pockets.
A girl's compassion towards it when it had been injured became a pretty cool part of the book.
If it detected weapons in the pockets or hands of eople it decided were not "friend" it would move faster than it could be seen and rip out the weapoon and take it home for its collection.
Totaly cool.
The author is Neal Stephenson, btw [memory is slow].
Ed