Twilio, which has built a platform supporting SMS and voice calling in apps from 40,000 developers, is adding VoIP to its arsenal of tools for third-party developers.

Its new SDK for Android, iOS and mobile web apps lets developers add two-way audio or Skype-like calling to their apps. Developers can add conference calls or basic person-to-person voice calls and it works regardless of whether users have two different types of devices.

“Developers can bypass the phone network, no longer needing phones or a 10-digit phone number, and embed an audio pipe in their web or native apps,” said Jeff Lawson, Twilio’s chief executive. Internally, Twilio employees even built their own intercom system with the SDK to allow real-time calling and conference calls between team members.

“Developers have been clamoring for 8 years to do things with Skype,” he added, expressing surprise that the company, which was recently sold to Microsoft for $8.5 billion, hadn’t taken a platform strategy on top of building a consumer brand.

Additionally, it’s hard to imagine that somebody won’t at least try to adding voice chat to a game to augment multiplayer mode, akin to what Xfire did for web gaming. Connections will cost a quarter of a cent per minute. Integrating voice functionality involves adding a few lines of code and less if the developers uses Twilio’s markup language.

Twilio, which raised $12 million from Bessemer Venture Partners, Union Square Ventures and 500 Startups in November, is probably best-known for powering the spate of group messaging apps that became popular at the beginning of the year like GroupMe and Beluga, which was bought by Facebook.

But its biggest verticals actually involve call centers and web directories, which earn revenue when they generate leads or drive customers to make calls to local businesses.