If you receive a message that says you need to calibrate your device, it means that something is throwing off your geo-position. First, remove any magnets or case holders or wallets that might have magnets that might be affecting your GPS, and thus affecting your Stops experience. Note also: magnets will affect most of your gps and location based programs. Next, hold your phone in the palm of your hand and begin to make figure-8s with your phone. This helps your GPS reset to the proper coordinates.