I love Twilio, let me count the ways. Doing flow control of an online or offline process from a phone is awesomely powerful. (Particularly cell phones.)<p>Here's a related example which I'm busy coding today: I wanted people to be able to record custom appointment reminders, but (following many years of supporting non-technical users) think microphones and MP3 encoding are probably beyond their ken. So instead, when you click "Send Mary Smith a custom reminder" on the site, it pops up a lightbox saying "Call 555-123-1234 and type in the code 1234", and when you do so the phone will say "Leave your custom message for Mary Smith's appointment on June 16th from 5:00 PM to 5:30 PM after the beep." Then, after doing so, your lightbox automatically closes and you get visual indication of success.<p>Bonus points: registering new numbers in Twilio is so cheap that I can trivially afford to give every customer their own call-in number, and tell them to put it on speed dial. Then I can use the same basic pattern for any number of tasks.