same dilemma here, i only have 1 key. i found some x5 keys on ebay...are these any good, if they can be reprogrammed?

From what I've read and heard from my dealer, the keys are coded to your VIN. The master key battery is not replacable and the master keys are recharged in the ignition while you drive. So you ought to use both keys regularly if you want to set the alarm and locks. Otherwise it becomes just a lock & ignition key. I also heard that dropping them may also lead to a bad battery.