The reason is that I don't need the display/computer functions of the iBike really (although some are interesting), I send all the relevant data to the Garmin (and this is perhaps even more so now the Gen III requires less fiddling about). The problem with two bar mounted / stem mounted devices is that it's all a bit cluttered and ugly. Which leads me to my second and perhaps more radical suggestion: What about just making a headless iBike for use with the Garmin Edge? It'd be a perfect accessory. Containing airscoop, processor and USB port - no buttons or display. The wireless could also be contained in the device. Being much smaller this really could just be mounted under the stem. Connect it to the PC via USB to configure?
Don't shoot me, these are just some crazy ideas that came to me out riding today
