SMS message to call back

Does anyone know of an inbound SMS provider that ties into asterisk? I am looking to make a txt/sms message to call back. Any help would be greatly appreciated.

If anyone else has already done this please post

I know that Voiptalk in the UK does this sort of service. Have a look at

I did it, but using GSM modem, connected to computer (with Asterisk) through RS232. I made application which listen COM port and when SMS came, I started Perl script - to make call file, check validity etc.