I’ve been writing window services lately and one thing I do is broadcast using Udp, service type, IP, port, other. (LAN only).
Then the calling service listens for what services to use and figures out the rest. I don’t have to configure the calling service.
It would be really cool if the iSms could broadcast IP, Port, modem info, phone number, etc. That way all my service has to do is listen and look for a specific phone number, for example, and bam off to the races. That way if IP or port gets changed I only have to change the iSms and not my service.
You could also reverse this where the iSms listens too. And always knows how to find the service it’s supposed to call.

Also, MMS capability would get great as well.