DuoDuo - two Saturn, two Genesis
It's called the DuoDuo. The idea behind it is that SNAC adapters for 2-Player Saturn and Genesis does not exist and a lot of customers ask about it so this would be the solution.
The DuoDuo is a Arduino based pcb that supports 2 x Saturn controllers and 2 x Genesis controller, one pair at a time.
Supported controllers will include the 3D controller for Saturn and Multitap for both Genesis and Saturn, among other things. More info soon...