You could also use the
Rhodium Keyboard Controller over at xda as noted above. This is a remapping tool that will allow you to map
any hardware key you like. You would be able to map up/down functions to the volume up/down keys in every app but the phone app for instance. See
here for more details. And on top of mapping my volume keys to up/down keys (except in the phone app) I also mapped "Enter" to the long-press of the hard 'BACK' key (to the left of the End key). I then use my vol up/down plus the long-press Back key to move up and down and select items.