Is there a way to get ad-hoc cross-platform (iOS, Android, and PC) device discovery for local multiplayer?

What I mean is something like this scenario: http://www.youtube.com/watch?v=csXYZf2vGdE

Multiple players, each with different devices (iOS, Android, PC). One player starts a game. The others can search and automatically discover his game and enter into a local multiplayer match. This would all be done P2P, without any dedicated game servers.

It seems that AllJoyn still does not have an iOS plug-in for Unity. However, there is an iOS SDK for AllJoyn. Since Unity uses C#, what's the difference between a plug-in and an SDK? Could you use the AllJoyn iOS and Android SDKs to make a cross-platform game with Unity?

Or is there another way to do this?