Booby traps are the best recourse clearly:
try to kick the bike over without the key? tazer to the b hole
try to roll it away? oops you just pulled the pin on a tear gas grenade
but really, its getting a new chain and a disc lock. one of the Manhattan dudes uses a gps that stays connected to the battery, and sends texts if the bike is knocked over, moved, or the sensor is cut out. yearly subscription though.