for a treadmill, i got the Sole F63. its the most stable treadmill i could find for $1000. its got a good size belt, motor, and its relatively quiet. no major complaints so far. its water bottle rack is not in a usable position, but i dont mind because it adds stability, and there are more cup holders up on the console. also, its heart rate monitor handles are a bit too low for me to use comfortably. but it comes with a chest strap if i really wanted to use it.
for output, i ordered a widescreen LCD monitor and an Ergotron LX wall mount. the treadmill will be placed alongside a wall, and then the monitor will swing out in front of it (from the side). the wall mount is really flexible so positioning shouldn't be a problem. for convenience, the monitor has built-in speakers. alternately, the treadmill has an audio input jack and speakers.
for input, i ordered an Ergotron LX wall mounted keyboard tray. i'm hoping this will let me easily move the keyboard out of the way when i want to just use the treadmill as a treadmill. the worry is that the wall mount might not be stable enough to let me use a keyboard and trackball while walking. that will be something i have to try to find out. the backup plan will be to build a small desk/shelf that sits on the arms of the treadmill to hold a keyboard and trackball. that is where the stability of the treadmill will really matter.