A cycle computer helps you make the most of your time on the bike. Trying to keep your average speed a bit higher or finish a familiar route in a new record time will give you the inspiration needed to push harder and get fitter. If you commute on the same route every day, a computer injects a bit of interest. Cordless computers are much easier to fit and look neater on the bike. If you're serious about improving your fitness, a computer with a cadence (pedalling rate) function will really help and these often read from the rear wheel, allowing them to be used with a turbo trainer.