Peer Calls is described as 'WebRTC peer to peer video chat' and is an app in the File Sharing category. There are six alternatives to Peer Calls for a variety of platforms, including Online / Web-based, Android, Android Tablet, iPad and iPhone. The best alternative is Jitsi, which is both free and Open Source. Other great apps like Peer Calls are Whereby (Freemium), Collabify (Freemium), Walkie (Free) and Astian Spika (Free, Open Source).
Jitsi (previously SIP Communicator) is an audio/video and chat communicator with full encryption that supports protocols such as SIP, XMPP/Jabber, ICQ/AIM, Windows Live, Yahoo!, GTalk/Hangouts extensions, as well as OTR, ZRTP, etc.
Walkie is a better way to communicate for distributed teams that don't want to spend all day in dry text channels. Voice Only A voice only communication tool that enables teams to communicate with emotion and purpose. Distraction Free
Astian Spika is an instant messaging service focused on speed, security and productivity. With great differences such as integration with Astian Cloud, support for video calls, calls among other features.