As far as my research goes this is available only if you live in North America ( US and Canada ONLY ). I did not find such a service with the European/Asian/Australian etc carriers.You can actually send an email to a number via a provider, and they will convert it into a text and send it for you.
This is a fairly easy process. All you need to do is : use default mail.app on your iPhone/iPod and know which carrier they’re with. And by they i mean the recipients:
- T-Mobile: phone_number@tmomail.net
- Virgin Mobile: phone_number@vmobl.com
- Cingular: phone_number@cingularme.com
- Sprint: phone_number@messaging.sprintpcs.com
- Verizon: phone_number@vtext.com
- Nextel: phone_number@messaging.nextel.com
If you know any other method, or such methods for the rest of the world please dont be shy and share them in the comments.