No, look at TextMarks.com or ZeepMobile.com for SMS. A mashup between a service like that and Twilio would be very cool, however.
Twilio is great for building the kind of phone apps you get when you call your credit card company to get your balance, for example. It makes programming an Interactive Voice Response (IVR) application a piece of cake. Once you learn the REST interface and the really simple XML syntax, you can use whatever language/platform you want to build your app and host it on your own web server. When a call comes in, Twilio hits a URL that you set up and executes your script.
I was able to set up a pretty complete voicemail/calling card application in only about three weeks of spare time hacking. Please check it out: http://ThisLineIsSecure.com. Twilio made this project absurdly easy.
