Instructable user Sailor Bob wanted to track his pedals-per-minute to set goals and get more out of his routine, so he turned a cheap $US10 bicycle computer (found at Wal-Mart, in his case) into a reliable cadence meter using some dollar-store magnets and a few cables. The hardest part seems to be setting up the LCD computer, but it’s nothing you couldn’t tackle with a little free time and effort. Hit the link for detailed installation and setup instructions.