They are everywhere. Increasing numbers of robotic vehicles are employed for a variety of missions on land, sea, and air. It has been primarily military uses that have forced development of their technologies and associated operational techniques.
Aerial drones have been very successful in the Iraq and Afghanistan wars and have become a standard element of air power. In the oceans, the autonomous unmanned vehicle (AUV) evolved more slowly, although the history is lengthy. In fact, torpedoes could be called the first AUVs, though they are not thought of as such.