Active Sneakers

Simple, take the usual training shoe design. Add microphones which detect all the noised made by said footwear, the scuffs, shuffles etc. Then build in small speakers which replay the same noise in the same direction out of phase.... thus cancelling the original noise.

Of course this won't work on a long floorboard creaking on a nail 4 feet away, but you can't have everything.

Criminals and assassins would be happy (actually, Homer Simpson had a pair of Assassins...).

It will also serve to stop Americans calling normal trainers "sneakers".