A few years back I aqquired this IS-Viewer64 for around $150, knowing that I probably never would be able to use it. Why? well as far as I know it needs a modified N64 for starters, and
second off it uses a SCSI interface.
My good friend "Shiggsy" once wrote
High speed debugging tool which allowed you to send a 96mbit image from a PC in under 6 seconds (2MByte/sec)! The price of this unit back in 1997 was about 1800$usd...
I've seen IS-Viewers with a wide variety of labels, so good luck to the variant hunters out there, you'll need it :-)
That is pretty much all the info I have about the IS-Viewer64 at the moment.