Oh yeah, that is in development. The idea is a stabalizing device like that on smart bombs would be placed on the back of a .50 cal bullet so it would adjust its flight path like a bomb does to hit the target.
Now it can't make sharp turns or anything like in hollywood or computer games, but in theory it would hit precisely where you wanted it to go regardless of wind and would be particularly effective against moving targets. Again, think about how a smart bomb works.
I have no clue if it is feasable or not but it's been in development since the late 90s I believe.