Wordpress plugin for sending SMS?
 

I'm looking for a wordpress plugin to send SMS messages. Basicly I'm looking for this:

1) Website vistor is interested in the content of post ABC
2) Website visitor fills in his mobile phone number and gets a custom message ABC
3) Website vistors goes to post XYZ and is interested again
4) website visitor fills in mobile phone number ands gets a custom message XYZ

Does this exist? For free or paying?