I know you probably worked hard on this, but I'm extremely disappointed that you might have just lifted Twilio's appointment script example (http://www.twilio.com/docs/howto/appointmentreminder), set up a billing frontend, and charging $79/month for this product. I wish you would've credited Twilio for much of the hard work.
As much as I want you to succeed, I don't know if this is the right way to do it.