A bit different, as it's mainly for voice - but I made an app 'Murmur : Bluetooth Group Calls' - that lets you hold group voice calls and message via a mesh of Bluetooth LE connections. It's available on Android and iOS. https://apps.apple.com/gb/app/murmur-bluetooth-group-calls/i...

Doesn't really get any downloads, so not sure there's much demand for this - but I use it with some shokz bone conducting headphones for talking to my wife when we're cycling (also for wrangling our two small girls)