Thank you both for your thoughtful replies!
Let me throw in some backstory - I was cleaning up some of my storage bins as my 1 year old son has been grabbing everything. I saw my Pokewalker didn't work and thought, "How can we make this timeless?" The random idea came to me, and my experience with this sort of thing is zilch. I have done some programming before but nothing of this sort.
Could we rip the software of the Pokewalker and create an app shell for an Android so that when it looks for input from the stepcounter, it uses the one on the device? As well as button inputs, IR (frequecies and ranges?), etc? If I have the program and what the triggers are for input and output, then all we need to do is find an app maker to tie it all together.
Am I dreaming too grand here?