It's a board that you plug into your NuBus mac. It uses LEDs to display things like the system clock, voltage rails, bus activity, system power status and ADB activity. It has what might be an ADB connector on the back. I can't however confirm WHAT exactly it is. Even my 2.0 software manual doesn't mention the card and the only real logic on it is four 7400 series chips. It basically gives you an immediate check to see if the machine is working or not but it isn't at all required to run all the tests in Snooper.

Also, Snooper will work with any pre-Intel mac running up to 9.2.2 however some hardware tests and especially the benchmarks will not give accurate results but it has a handy tool to display slot info, PRAM contents and a few other things.