The beauty of a metronome is the opportunity to learn slow - in rhthym - and then slowly speed up - until a complex piece is mastered.
It should be very simple to use basic software - (at different tempos) to create mp3/ipod tracks.
Personally, I like the old reverse pendulum windup.
Musical recordings - for syncopatic Latin beats - listening-tapping - over and over and over - Eyi Yie Yie! Very difficult! (for me)