Electronic Door Lock keypad with Arduino

my doorlock has a remote that came with the unit. If you picked that one up you could just use the arduino to simulate a button press. it may be the easiest/cleanest solution

http://www.smarthome.com/51895BN/MiLocks-BQF-01OB-Touchpad-Deadbolt-and-Remote-Control-Handleset-Combo-Oil-Rubbed-Bronze/p.aspx

i believe the remote even has an easy access for a wired trigger