I remember hearing about those along time ago. I also remember hearing about homing bullets that target in on laser signals. Those were neat. They might be able to go around corners. The head of the bullet is a half sphere and a cone, and has a sensor on the tip of the cone, and a swiveling motors on the ball (or tendons or something) that move the head around to turn the bullet's direction to wherever the laser light is. In the demonstration they had a sniper take out an M1 tank at quite a distance, with 1 bullet, 1 measily low grade bullet that can home. He fired it, and another guy pointed a laser for it to home in on, onto the tank's magazine (which is barely visible). Boom.

I dont know the actual caliber of the homing bullet, but it was fired out of a standard rifle.