There is speculation that Apple is planning a interface like iTunes that would add value to owning an iPhone/iTouch.
This software platform would allow the planning and tracking of fitness routines among other things. Ninetendo's Wii added a fitness component (Wii Fit) that has extended the value proposition of its gaming system as would an Apple designed lifestyle package for its iPhone platform.
Up to this point the existing fitness monitoring systems which I am aware of are limited and/or expensive. Suunto offers a watch, heart monitor and software that tracks overall fitness, but is limited only to PC's which I have found it to be buggy and is not worth the headache. So I would welcome it if Apple designs a usable system of lifestyle that allow archiving fitness data.