What issues did you run into? Were you able to find open source libraries to take away some of the grunt work? How deep did you have to dig into the bluetooth stack?

For context, I'm working on a side project that involves a game written in Unity that will need to talk to devices over Bluetooth LE (and ant+). What I've found is incredibly disheartening so far. I want the game to be cross-platform, but it seems that every platform has it's own bluetooth stack, and even within a given platform, there may be N bluetooth stacks (looking at you Windows). AFAIK, nobody has written an open-source library to abstract away the platform specific details and just let apps talk to bluetooth devices with their chosen service. Also, the official bluetooth docs are really good, but I'm surprised there isn't a Bluetooth SIG that writes and maintains official bluetooth SDKs.

I've been heads down in the weeds on the problem for a week now and I feel like just solving the device connection problem is going to be a massive undertaking. I'm hoping to hear some inspiration from others, or find some tools to ease the process. Seems like a lot of people run into this problem online, but nobody has a good solution.