Nintendo Wideboy 64 AGB
Developers tool to play and debug GameBoy Advance, GameBoy/GameBoy Color cartridges though a Nin64 system

This is a developers cartridge the Wide-Boy 64 AGB made by the only authorized developmental tool creators for Nintendo items, Intelligent Systems. 
This cartridge would plug directly into a Nintendo64 game system to allow for Gameboy Advance, Gameboy COLOR, and Gameboy cartridges to be displayed through a full monitor and which could only be controlled by using the Nintendo64 controllers. This would allow for more people, developers, producers, and decision makers to see and experience the  game play and action in a larger presentation. These units would also allow for individual sprite manipulation as well as better screen shots to be taken. These are also used for game shows in which the companies would want their games to be displayed on larger monitors so more people could see the game in action. 
These units could only be bought directly from Nintendo at a cost of $1400.00 each, if you were a Nintendo authorized developer or magazine publisher.