I don't.
We got rid of the cell phone I kept around in case I should get stranded somewhere or have an accident about a year ago, because cell phones are so ubiquitous that I am sure even if I don't have one, someone else in the vicinity will, and the chances that I'll end up somewhere where there is NO access to a phone of any sort is so remote that the "in case of emergency" justification for the $30/month just didn't hold water.
I don't like talking on the phone much to begin with so I never used the cell phone except in rare situations, and the idea of receiving text messages on the phone is enough to make me scream. Forget the obnoxiousness of the abbreviations used in text messages (which in itself is enough to make my eyeballs bleed) someone being able to repeatedly intrude on my attention like that would make me nuts. I don't have a IM client on my computer for the same reason. I'll take phone calls and have a meaningful real-time conversation that is actually over when it's over, or I'll answer emails at my leisure, and that's it.
I struggle enough with ADD to begin with, constant interruptions from IMs or text messages would make my life pretty well non-functional.
Edited, Jan 14th 2009 7:34am by Ambrya