From across the pond comes an interesting item. Seems the folks at FN Herstal over in Belgium have developed a tattle tale for your gun. The version they talk about appears to fit in the grip of a standard AR platform, but can be adapted to any gun.
Now, your local constabulary can stop you and plug your gun into their little "reader" and be able to tell exactly where you've been, what you shot, where you shot at, and what you had for breakfast for the last 3 days (ok, I made that last one up).
This ought to give you pause. As is hinted at in the article, the limits to this technology are scary. This is what they've been waiting for. Smart gun technology. The only thing missing is the remote off switch so if you don't have 'permission' to use your weapon, you won't. You can bet it won't be far away.