jointtech:
these are already out there. if you don't own the lock already you aren't going to save any money.. if that's the point
http://www.amazon.com/Schlage-Wireless-Keypad-Entry-Bright/dp/B001NEK6HY
that lock must be $50, plus you need an arduino at $30. plus misc stuff, plus time. Is yours going to do something different or better? Or just a cool project to play with.I think it would be much cooler if you use some kind of manikin (sp?) hand that actually pushed the buttons when you got close. That would creep somebody right out
Thats just an addon. heres the kit you would need: http://www.amazon.com/Schlage-Wireless-Keypad-Starter-System/dp/B001NEK6LU/ref=pd_cp_hi_1
But in any situation, its a project and i like to do things myself so i know how it all works 