I'm trying to use Twilio to send and receive SMS on my iPhone. I've gotten inbound and outbound calling set up following these instructions. I'd like the equivalent instructions for SMS. I'm presently using Zoiper as a SIP client, but that's flexible.
The phone number configuration page (from here click a phone number) has a section called "Messaging" which allows one to configure a TwiML bin. However, I haven't been able to find any documentation about how to configure SMS over SIP, let alone TwiML code.