This may be a better idea for 'Join' but I couldn't find a place like this for that app. Sound. The ability to send whatever sound is playing on one device to another device and possibly mute the sending device so the sound only comes out of one. Being able to use the microphone in a similar way would be helpful. There are apps out there that do some of those things in a limited fashion but I believe you could bridge the gap. My over all goal is a motion activated intercom/doorbell.