Where can I find a keyless padlock containing two AAA batteries that opens automatically?

Question

Where can I find a keyless padlock containing two AAA batteries that opens automatically when you push a button on a little handheld device that also has a battery and a red light comes on and energizes the lock?

Answer 1

This is probably an infrared lock, like the one below.
However, what happens when the lock runs out of batteries?

http://conch-haian.en.alibaba.com/product/0/50648523/Infrared_Reomote_Control_Door_Lock.html