I buy this device to help I pace my run . it do a decent job at it when it can get the necessary signal . unfortunately , it lose signal pretty often . I be look at the output of the run log program , and it show that I reach a run speed of 20 mile a hour at one point . well , I can hardly get up to that speed on a bike . the error be obviously cause by the lose of signal . because of this , the device be good but not great .