I have read about this device and even found some info like pictures and box scans, but it seems as though it is pretty rare.
If I understand correctly, this device allows you to save and restore machine states from system RAM in order to have a quicksave capability like that which is found in emulators.
Does anyone know how the device works and makes this happen?
Are there schematics or more detailed info available for this device?
Any leads on where to get one?

I would love to make a cart or mobo expansion that would allow me to do this on an NES, and maybe to integrate it into some sort of advanced multimapperdevkart.

huh? where you read that part about saving/restoring machine states

http://www.atarihq.com/tsr/odd/scans/gar.html

has a high-level description, some pictures, and a screenshot of the control menu.

Also, any ideas on slow motion? if you crowbar and strobe the Vertical Refresh Interrupt line, could you make a game arbitrarily slow? Is this how it works in this system, prolly?

i'm not sure how the slow is done - i mean to slow all games down you must surely be intercepting the pc?, well if you can do this you could maybe make it do every instruction twice - naturally halfing speed?
i'm suprised that the device can read/set all the cpu registers - which it needs to do to 'fully' restore a game from any point
maybe someone knows more about this sort of control - its certainly interesting - have you tried contacting the wesite to ask them where they got their info from