You could do phone sex (voice only) with WebRTC with TLS (SSL) encryption on a HTML5 webpage '
app' on a smartphone now. Anywhere in the world where there is a 3G/4G connectivity (near everywhere).
Phones and the Internet are very integrated now.
All you need is an SMS messaging switchboard. (Hook up website.)
And a billing gateway/wallet
You don't need 900 lines and TV ads today