I remember when I was deeply involved in working on my dissertation, I would have dreams in which I was reading an academic article, and I grew frustrated because the text on the page would keep changing — apparently my dreaming mind didn’t have a buffer big enough to store that much text all at once, but I was able to note that it kept changing.  But this article from the Atlanta Journal-Constitution describes how a teenager young woman managed to send text messages while sleeping:

Castillo’s multimedia
message to her boyfriend on her Pantech C300 phone involved 11
different steps, not including the typing. First, she had to select
“Menu,” then “Messaging,” type “New,” then select “Multimedia message,”
then punch the “Add” button and the “add text,” before entering her
garbled message. Afterward, she had to press “OK” twice, scroll to
“contacts,” find the e-mail address on that contact, select it, and
press “Send.”

“Not an easy process but once you get used to it, it becomes very easy,” Castillo said.