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Just tried StepTracker.. didn't seem very accurate. If you're looking for a good Bike route tracker I like CycleTracks.
 
Try iTreadmill. Worked well for me. The first run/walk/jog might not be accurate (in distance), but by correcting it, it will get all future distances correct. It has tonnes of features too, like history charts. Worth the cheap price ($0.99).
 
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