How to recreate square waves over wireless in 'real time'
user1850479's suggestion seems the most workable. Filter the square waves down to sine waves, but with the zero crossings in the same place. Then you can either broadcast them on a shortrange audio solution if you can find one that works at up to 100kHZ - not bluetooth, since that subjects you to compression and latency. Or you can build your own small FM transmitter in a suitable band.

Have a look at the EU radio bands allocation; you'll end up picking 434.04-434.79MHz or 863-865MHz at low power, given that you'll be using 100% duty cycle for continuous transmission.

At the receiver end, use a comparator with hysterisis to reconstruct the square waves and identify the zero crossings. Or you can do it in an ADC if you prefer.