The wheel lock just makes it more difficult to steal the rear wheel. With a proper U-lock they're quite useful. They're are relatively weak when compared to U-locks, but they usually go round the rim and leave little extra room for tools/leverage. Axa-Basta has several decent models (see "Framelocks" and "Click locks").

We do have some bike stand designs with a length of chain attached. The idea is to take the chain through the rear wheel lock, preventing anyone from carrying the bike away. Usually there's enough chain to take it through the front wheel too, basically securing frame and both wheels. Still I think the rear wheel lock alone is for low risk areas only.

--J