The Delphi from Blackburn can do 2 bikes although you need to get the mount for the 2nd bike. As of right now I only have the computer on my Road bike and not commuter. However I should be receiving my Garmin Forerunner 205 today which can do bike so i will just be using that from now on.

I say if you have the money go with the GPS that way all you have to do is have the device with you and there is no set up for each bike. Gen you can get some decent deals on ebay.