Rebtel’s free SDK for iOS and Android devs to integrate VoIP calls into their apps has launched with dating app Maybe.

Rebtel tested the functionality in a beta trial with more than 20 developers, including TGTHR, Agile Dimension, eXeltior, as well as MobisleApps, creator of the Maybe app. Users will (slightly scarily) be able to make free anonymous app-to-app calls to potential dates.

The SDK, which works over wi-fi or 3G, now includes support for iOS background mode and audio playback controls for playing ringtones and other sounds.

“Adding free voice functionality is a critical component for our dating app, and we’ve been extremely impressed by both the call quality and the ease of integration,” said MobisleApps CEO Fredrik Olofsson. “We think this will be a huge value add for our users who want to be able to talk with one another anonymously and for free, while giving us a valuable tool to acquire news customers and drive user engagement.”