This is a paid asset, but now you can download Android Bluetooth Multiplayer (Basic) Free.
Detail this asset from Unity Store: Original Link
Android Bluetooth Multiplayer (Basic) v2.1.3.1 (Latest version)
Ever wanted to add Bluetooth multiplayer to your Android game? Then this is the one and only plugin you will ever need.
Android Bluetooth Multiplayer allows you to add Bluetooth multiplayer to your game with just a few lines of code. It is fully compatible with Unity’s built-in networking systems. What this means is that you can easily reuse your networking code for Internet and local gaming with minimal changes, or use any of existing tutorials about Unity built-in networking.
Adding Bluetooth multiplayer to Android game wasn’t possible before… And now it’s made easy!
Features:
– Fully compatible with Unity built-in multiplayer (both UNet and legacy). No need to write special networking code!
– Documented demo examples and components to get you started immediately.
– Powerful API to cover even advanced use cases.
– Comprehensive documentation included.
– Supports Unity 5.2 and newer. Pro license is not required.
Pro version includes full plugin Java source code.
Additional information:
Forum discussion thread
PDF documentation
Android Demo APK