We train a body of finger and hand/wrist locks in
Modern Arnis. Though the goal is usually to prompt a change of focus from your opponent than any long-lasting pain compliance.
I've seen it in action many times. People (especially untrained) who find themselves in a pain-inducing lock will naturally try to move in such a way as to minimize the pain. This can be anything from an attempted rapid retraction to a full-on posture change (most common). But one thing that is almost universal is that a "good" finger/wrist lock will not only get your opponent's attention, but will likely make him change his initial course of action.
One thing we don't do with locks like that is try to maintain control. We put the lock on just long enough to create an opening for a strike/throw/whatever. Maintaining a small joint lock on a non-compliant opponent for any length of time is exceedingly difficult.