Well, first you get a bicycle. Then you connect your PDA to it as your speedometer and far more. Besides the obvious advantages of a (relatively) huge display area and whatever statistical processing you might want to come up with, organized (group) rides have these things called "cue sheets" -- a list of waypoints and turns by cumulative distance. If you put the cue sheet into the PDA, this setup can tell you how far it is to each next turn.
what I would do with a PDA
Well, first you get a bicycle. Then you connect your PDA to it as your speedometer and far more. Besides the obvious advantages of a (relatively) huge display area and whatever statistical processing you might want to come up with, organized (group) rides have these things called "cue sheets" -- a list of waypoints and turns by cumulative distance. If you put the cue sheet into the PDA, this setup can tell you how far it is to each next turn.