The PiSquare is an accessory for the Raspberry Pi that allows you to connect HATs wirelessly. Not only is it possible to use a HAT without a physical connection, you can also pair multiple PiSquare units to your Raspberry Pi simultaneously over Wi-Fi.
https://www.notebookcheck.net/PiSquare-Affordable-accessory-for-Raspberry-Pi-HATs-launches-for-under-pound10.612696.0.html