So you got the good position, (side control) take kesa gatami...
I'm sure any number of BJJ players might appreciate this particular arm lock and it's variations.
See if we can draw the MMA guys down here and rate the thread if you like this little trick.
It's a very simple armlock but it will destroy the joints if you're not careful with it, eh?
Give your friends time to tap out and don't torque it too much.
Think what else you might try with his arm isolated like that?
Could you release his head and udegarami his other arm at the same time?
Hmmm?
Maybe you just want to punch his face in? Lock out the arm and go to it!
http://www.youtube.com/watch?v=RW7CpZUpMyE