The coming is enough. That is what I use to manage the ring tone. I haven't tested but, like you, I think only works for "tel" calls.
What I accomplished so far is telling telepathy to use a "service" (account: tel, spirit, tor, ...) and start a call to a number or start the "sms" messaging ui for the phone number. It is really nice and seamless... I know using qt mobility and/or tpsession you can also send a sms directly from your application (not start the messaging ui). What are you trying to do?