This is great!<p>Thanks so much for sharing the code, it's extremely helpful.<p>I've thought about making something similar (notifications for certain events via SMS) and I'm wondering if you know if Twilio can charge a fee to the end-user for every text? i.e. if for example I say "Subscribe to get an SMS every time there is a tornado in your area, for 50c per SMS" (I made that up, BTW)