hugo19941994 on the Shmups forums has just posted what I believe is the first English review of the new 2.4GHz wireless kit for Sega Saturn controllers: https://shmups.system11.org/viewtopic.php?p=1333979#p1333979
This kit replaces the innards of your stock Sega Saturn controller with it’s own wireless kit and connects to a dongle that plugs into the cartridge port on the Saturn. The kit can be purchased here:
This seems like a great solution for people who want to use their original controllers, but add wireless functionality. I’ll be interested to see how they compare to the upcoming RetroBit wireless controllers!