Here's a background video I did on the hardware: https://www.youtube.com/watch?v=MFcrNk33_io
It's DIY, 3d-printed hardware that's incredibly extensible, and has a decently designed abstract communication protocol that I've ended up pointing other DIY creators at. Keeping up with everything the hardware can do while also trying to make it work with our generalized commands is a challenge, but it's a good challenge, because we don't see a ton of innovation from the large commercial manufacturers.
Least enjoy: We support over 500 devices now, so this is just a whole classes of devices at this point heh. There's a lot of hardware we support that's just not very good to begin with, and users can't tell whether it's our library or the hardware hardware that sucks. Then there's the hardware that makes very... odd decisions about how to do things. For instance, there was a brand known as MuSE or Lovespouse that's been popular for the past couple of years. Instead of creating a bluetooth connection to the device, the device acts as a host and listens for advertisements w/ specialized data in order to set vibrator power. Not only is this easily hackable (there was a bunch of articles about someone doing exactly that with a flipper zero last year), it's damn near impossible for us to implement cross platform support for, as advertisement creation in BLE is wildly different across platforms, and doesn't even exist on iOS (the company themselves only shipped on android, where buttplug works on win/mac/linux/android/iOS). On top of that, the Lovespouse devices were extremely cheap ($10-30US sometimes), so we had users buying them then asking if we supported them, and all we could say was "nope".
Problem is that it's non-standard, so every device packages the data a different way.
There's a god damned heart rate profile standard in the bluetooth spec AND YET I'm not sure I ever actually worked on a device that used it. :|