Flyspy.

FlySpy is a short-thriller about a young, genius deviant called Greg, who has made a wirelessly controlled drone in the form of a fly with a camera in its head. Everything the fly can see Greg can see. He is deeply obsessed with his ex-girlfriend Haley so he spends his time secretly watching her through the eyes of his tiny robotic partner in crime. But when Greg witnesses Haley’s violent new boyfriend, John, abusing her, it very quickly becomes clear that for Greg, simply watching, is not enough.