There is no better way of getting fitter, stronger or faster than – well – training. And training gets a lot more effective if you can accurately measure the distance you travel, and at what speed. There are myriad wearable devices out there that purport to do this, but most activity-trackers are little more than souped-up pedometers, neither particularly accurate nor consistent.
That is not to denigrate activity trackers. If your goal is simply to nag yourself into burning more calories each day, a Fitbit or Jawbone will definitely be a good purchase – cheaper than any of the GPS-enabled devices we review here.