I have a Shimano ready Power Tap wheel that I no longer use This is one of the first ever models There are 2 computer attachments ,one with USB ,the other with a Serial port This is a wired unit and has the shark fin pickup See the enclosed photo This unit is best used by someone that likes to tinker and has some tech savvy Software to operate it is free from Saris This was on my dedicated trainer bike and saw good service but would occasionally drop data Saris told me the unit was no longer serviceable as too many changes have been made to newer units With that in mind the price is right at 35$ to the right person

Ben D