This is a great project. Sticking magnets on to a baked-ban can allows you to program beats and arpeggios. I was thinking of making a rotary version of the BeatBearing at one point. Glad to see that something similar has been made! Blurb from youtube video below:

One empty baked bean tin, some lego and a stack of little magnets… stick magnets on the tin and slide them about to ‘program’ the sequencer, then grab hold of the ‘transport control’ and crank away…. The breadboard contains 5 hall-effect switches and a PIC16F688 to generate MIDI note on/off information. This is piped to Reason in the first half of the clip and to a Dave Smith Mopho synth in the second half.
I reckon with a baked bean tin about 16ft in diameter and about 25,000 magnets you could dump your sequencer software.. and you’d be getting some good aerobic exercise to boot :o)

[via:Synthtopia]