In 2001, the Court ruled against the government in a case involving use of a ground-based thermal imager to detect an indoor marijuana growing operation by measuring the temperature of the roof and outside wall of a house.

FORBES: Will "Drones" Outflank the Fourth Amendment?

It packs a pair of HD cameras along with a thermal imager and can stay aloft permanently, in theory, thanks to a microfilament tether attached to a ground station -- which also makes it impervious to weather, tracking and interception at the same time, according to CyPhy.

ENGADGET: CyPhy Works reveals tethered flying bots that can spy on you indefinitely (video)