One who spends a great deal of time sending text messages.
text + -aholic, extraction from alcoholic
My grandchildren are not quite textaholics, but they do use text messages as their primary mode of communication, almost never checking email at all. The difficulty with texting is knowing when to stop answering the latest in the string of one word responses.
The odd thing about the crossover from email, my base method for communication, to text messaging is wordiness. Typing with my thumbs DOES NOT WORK! I must poke along with one shaky finger instead of typing with all my fingers on a laptop keyboard. I generally want to say much more than I can get done with text messages.
Mostly I use phone text messages to confirm pickup times for relatives coming in to the airport or after school pickup plans. Interestingly, I think I do use text messages more often than phone calls at this point.