I know about the two devices thing, but the ipod touch is so damn thin you don't even know you're carrying it.
it may be a bit pricey up front, but keep in mind there are a TON of medical apps on it, and you are not paying a data plan so you are saving BIG time that way. It's a one time purchase for about 200 for the 8 gb version, and that's it. Trust me, well worth it.