Ah right - I don't really see that as an issue (when do you ever want to split them in a way the cable becomes problematic? also you now have two individual units to hook up with battery)

I guess this is why you don't really see many attempts.

But maybe something like this will do the trick?

https://wiki.seeedstudio.com/Grove-Serial_Bluetooth_v3.0/

I’m very broad so my keyboard is split wide, it comes almost to the end of the cable so having two wireless halves would make a nice difference. The shield looks promising, but with all of my other projects I just lack time to hack together a keyboard.

I'm using an Ergodox EZ which I really enjoy and I'm hoping wireless plus a trackball is in the next iteration. Even just being wireless (or a wireless add-on) would be great.

That would be epic. I asked the Ergodox folks about it and they said they’ve experimented with a wireless Ergodox EZ but there’s problems with latency with the two halves being wireless. So I’m skeptical that they’ll produce anything soon.