I found this:
<div id="b-sms" class="b-mobile"><a h-ref="sms:?body=Hi%2C%20check%20o
ut%20Niniane%27s%20Blog%
20at%20niniane.blogspot.com">Send As SMS</a></div>
   in the bars of blogs hosted on blogspot.com
A new feature coming by ?
The toolbar already enables this by the way.

[Trimmed line. -Philipp]

I think you will need to have to Google SMS installed.