Twilio is an API (application-program interface) for developers working on mobile platforms. It provides tools to communicate via SMS and voice, and to route telecom traffic through providers and past national borders. It is at once highly specialized, in that it is designed expressly for telecommunications programming and nothing else, and yet it is also versatile, providing tools to communicate in the mobile arena where the Internet itself doesn't normally reach. Though currently not 'complete' as of this writing, Twilio seems well worth trying for developers of mobile apps everywhere.