Although, I am pretty in touch with most everything when it comes to texting, I was stumped, so I turned to another innovative colleague, Celine Azoulay. She pulled out her trusty Periodic Text Message Table which she purchased at Staples. How great is this? A handy quick guide to support those of us with DSL accents.
Here it is.

While it doesn't have "SMH," (I turned to Google for that), it does have many common text message symbols like MYOB - Mind Your Own Business, JP - Just Playing, NMP - Not My Problem, WFM - Works for me.
And, as for my former student, translation:
"Shaking My Head" at this heat wave.
TTFN XO
TIE
Translation:
Tata for now. Hugs and kisses.
The Innovative Educator