I had no idea that BJJ artists trained wrist locks until I read this. Maybe wrist techniques aren't as hit-and-miss as I first thought.

GrappleMonkey

Especially the last video on the page involves a wrist lock submission win in a BJJ tournament.

They are trained sometimes. The problem is that in tournaments, wristlocks can be somewhat of a grey area. Depending on the rules, they may or may not be legal. Most people avoid them in tournaments because they don't want to get disqualified for pulling what may be an illegal move.

Roy Dean is a great resource on wristlocks in BJJ. He is a black belt in Aikido and BJJ, and he has a DVD out about blending the two together with an emphasis on wristlocking from standing and on the ground:

They can often be great for making another submission more effective, say if someone is really fighting a pressing armlock. In the tournaments I do you can use them, I believe at either beginner or intermediate and up.