I had no idea how to describe Twilio, so “phone app proxy service” was the best I could come up with. It’s probably nowhere close, so let me explain what Twilio does.

Register for a Twilio account, and you’ll get a phone number. People calling in to your phone number will trigger Twilio’s server to hit *your* server; specifically, a unique URL you give Twilio. Your URL will return back some specific XML which instructs Twilio to play a message, say some text, or ask the user for some input (key or voice). Twilio will then send the user’s input back to your URL, which you can then parse and send back more XML to instruct Twilio which step to take next.

That’s it. You can build your own phone-driven service without investing in any hardware and very little software. Cost is 3 cents per minute, which is very reasonable in my view.

What sorts of apps would you build with such a service? I’ve got some ideas of my own, and will let you know if/when I build any of them.

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