He and his colleagues have now developed a range of vibrating mini electric motors known as tactile actuators, or "tactors", and tested them in various configurations. "What's best is a belt around the torso with eight tactors signifying the eight cardinal directions."

The tactors vibrate at 250 hertz, which is just enough to give a gentle but noticeable buzz around the torso at regular intervals indicating the direction in which the soldier needs to travel to reach the next waypoint.

The belts are hooked up to a regular GPS device to access directional information, as well as an accelerometer and digital compass. These mean the device knows which way the soldier is facing, even if they are lying down. "As long as you are going in the right direction you will feel it on your front," says Elliott, who will be presenting the technology at the Human-Computer Interaction conference in Orlando, Florida, in July. "As you get to within 50 metres of the waypoint all the tactors start to go off, and within 15 metres they will quicken."

Besides directions, the tactors can communicate commands such as "halt", signified by the front, back and side tactors pulsing simultaneously, or "move out", when they pulse from back to front, almost as if they were pushing the soldier forward.

While commands could be sent from base, Schmeisser and Elliott are also working with a company called AnthroTronix, which has developed a glove that has integrated accelerometers to detect hand gestures. The hope is to allow a platoon leader to be able to communicate with their squad while out in the field through standard military hand gestures sent wirelessly to their belts, says Elliott.

Previously.