US military unveils 'smart gun'. While this has been around, I hadn't realized they were already in use as of this last summer. This is an amazing piece of hardware. The following description is off of wikipedia.
The XM25 is an airburst grenade launcher derived from the XM29 OICW.
It fires 25 mm grenades that are set to explode in mid-air at or near the target. A laser rangefinder in the gun is used to determine the distance to the target. The user can manually adjust the detonating distance by up to ten feet (3 m) shorter or longer. The gun automatically transmits the detonating distance to the grenade in the firing chamber. The grenade tracks the distance it has traveled by the number of spiral rotations after it is fired. These features make the XM25 more effective than traditional grenade launchers at the task of hitting targets that are behind cover or dug into the ground.
The system has been developed by Heckler & Koch and Alliant Techsystems, while the target acquisition/fire control is developed by L-3 IOS Brashear. The most recent deployment plans call for a purchase of 12,500 XM25s at a projected cost per weapon system of $25,000.
In the summer of 2010, the U.S. Army began field testing the XM25 in Afghanistan. The initial per unit cost of the early models range from $30,000 to $35,000. The army plans to purchase 12,500 XM25s in 2011 and have them fielded by 2012, enough for one XM25 system in each infantry squad and Special Forces team. 
According to U.S. Army project manager for new weapons, Colonel Douglas Tamilio, the rounds for the XM25 will cost about $24 apiece. 
Alliant Techsystems has indicated that the rifle may later use bullets with smaller explosive charges which will stun opponents rather than killing them.