Alberto -
In the States, all of our cell phone carriers associate an email address with a phone number account. For instance, for the phone number 123-456-7890, the email address could be 1234567890@messaging.sprintpcs.com (Sprint), or 1234567890@vtext.com (Verizon), etc. So you could just send an email to the address, but you would need to know what the address was, or at least the domain, and the phone number.
I know there are some services you could subscribe to in order to get all of the current and up-to-date text messaging domains for the various carriers, or you could just add them to your app as you come accross them.
Hope this helps!
Regards,
Flint