I keep being tempted by smartphones. To ssh from my phone and check email  and go on IRC would be a boon. A dangerous boon, but I keep seeing things like Nokia N900 has reviews like this...
"If the idea of hacking your phone down to the command line with the manufacturer's full approval sends you into paroxysms of joy, forget reading the rest of this review and just buy one now. This is the ultimate Linux geek phone."
...and it gets harder and harder to resist. It would certainly teach me how to package .debs (the phone's OS is Debian-based), which would be a useful experience for comparison (while I'm still new enough to making rpms to be able to feel the newcomer's "what am I supposed to do here?" pain).
I have different criteria for my phones than most people do, I suspect. I can't hear much, so I don't really use it to make phone calls; I'd rather use it as a portable text chat client. SMS, IRC, various forms of IM... have them all thread into the same interface (I like irssi). I wonder if I could do this on a non-mobile device by using an assortment of different proxies like bitlbee. Basically, it'd let me read to listen, type to talk. Bonus points if I can link a bluetooth keyboard (fold-out?) to the device so I can type back faster.
For when I do make phone calls, it needs a decent speakerphone - I'll sometimes listen to phone calls by putting the speakerphone rather than the earpiece up against my ear, because the speakerphone is much louder and I never liked taking calls with my hearing aids on. I couldn't care less about ringtones, but it needs a powerful vibrate because the shaking in my pocket (sometimes - I wear pants with loose pockets) or the phone clattering on a table or atop an empty cereal box is what will tell me that my phone is ringing. I don't care about games, can live without a music player, and ssh should give me access to any apps I'd want to use.
1.5 years 'till my next phone contract renewal, so there's plenty of time for both the hardware and software to evolve on this before I lay my simple flip phone to rest. (It makes calls and does SMS and that's all I need right now).
 For sanity, this means I'd have to switch back to either mutt or pine first. It comes down to which one is more tweakable (to me) - I'm guessing that means mutt is going to win, but I dunno. I could also try out muttator... so many things to experiment with, so little time.