From the BBC:

A newly-developed heat-ray gun that burns the skin but doesn’t cause permanent injury is now with US troops in Afghanistan.

The Active Denial System (ADS) is a non-lethal weapon designed to disperse violent crowds and repel enemies.

It uses a focused invisible beam that causes an “intolerable heating sensation”, but only penetrates the skin to the equivalent of three sheets of paper.

The discomfort causes whoever it’s pointed at to immediately start moving away. They often scream but the US military says the chance of injury from the system is 0.1%.

It’s already been tested more than 11,000 times on around 700 volunteers. Even reporters have faced the heat-ray.

Interesting thing about tech like this is what happens once you improve it. Think about computers. Effectively, since the first difference engines, computers have done nothing but calculations. The only things that have changed are that the calculations got more abstract and complex, and the devices themselves got smaller – massively smaller.

Right now the ADS is mounted to a mobile armored vehicle. Imagine, instead, the ADS as a device implanted into, say, every street lamp in a city. Instant riot control. Or, to the wheels of a car. Instant car jacking defense. Or what about to the buttons on your clothes? Personal protection.

The ADS as it is now is little more than an expensive PR stunt, but what could be done with the tech in twenty or thirty years, now that’s the interesting stuff.