Has anyone bought/used/returned one of these? Its supposed to do (among other things) speed, avg speed, and also cadence. I tried to set mine up last night on the bike but on the commute this morning it didnt register an RPM, cadence, and my speed was apparently 3.8 mph. Is there a trick to set these things up? Ill try and get some pics up of the system as it is at the moment, but Im thinking of cutting all the cable ties and sending it back if it isnt going to be at least slightly accurate.