I used to do this back in 2005. Forgive me if something has changed in the intervening years.<p>There was a rate limit for receiving and sending SMSes via the hardware approach. My experiments yielded 1 per 20 seconds iirc<p>In the end my implementation purely received via hardware and exited via a bulk SMS provider like clickatell<p>clickatell at that stage allowed big users to set the &#x27;sender caller id&#x27;. This was loved by spammers unfortunately so the providers became much more cagey about allowing that feature.