I discovered the BTH app a few days ago and it was perfect timing. I need it to control my Home Assistant setup when I am not home. The service is great! On Android I set up the tunnel and configured it to only connect for the Home Assistant app (to save bandwidth and such). I then shared the connection with a friend and that works too.
My question is this: The shared tunnel on iOS is not shown in the BTH app. So there is no way to limit the BTH app to Home Assistant. Is this a bug in iOS or a limitation of shared tunnels?