This makes me nostalgic. The first homebrew app I ever released[1] helped you pick combination locks with the help of your Playstation Portable.

Looks like the original site that described the algorithm is long dead, but the gist was that once you have the first number from a Masterlock (which you can listen for) the search space of the second two can be reduced with a pretty simple algorithm and so there are only a few dozen combinations to try.

[1] http://forums.qj.net/psp-development-forum/7427-release-psp-...