In case you don't have your own bouncer to guard your room, Steve Hoefer has invented has invented a device that will unlock your door if someone knows the correct "secret knock"!
If someone knocks out the wrong code, the mechanism ignores it and door stays locked. It can also be reprogrammed if the correct knocking-series gets into the wrong hands (har har).
ps. I bet it could also be helpful for those of us who have locked ourselves out on occasion!