In terms of SMS, couldn't you use any odd website that offers SMS sending (eg. one of Betamax Sites)... as long as you can surf the net?
The other queston I had, have you ever tried the SvSip (or SipVoip as they are calling it now)?
See
touchmods.net Weblog
Repository at
http://touchmods.net/rep.xml
It was around before Fring made their soft available for the IPhone...