The correct answer should be, “not much at all”. Wheel locks, like any other component of a layered security system, simply slow down thieves or make it more inconvenient for them to steal you wheels and tires. As the above video shows, they can be defeated with simple hand tools and little bit of practice. The good news is that hammering a socket onto a wheel lock creates more than a little bit of noise, so you’ve got a chance of hearing someone trying to steal your rims. On the other hand, they could just use a master key, which really doesn’t make any noise at all.
The moral to the story? If you drive a car with nice wheels and tires, be careful where you park it. If you want to be absolutely safe, you’ll need to construct an underground bunker in your backyard, complete with alarms and video surveillance. If you want to be reasonably safe, park your car where you (or your neighbors) will notice suspicious activity.