This device takes advantage of both the GBA and DS game slots, the $20 "PassMe" mod chip for Nintendo DS "redirects the DS to a GBA Flash cart, so you can run your own programs... on the Nintendo DS. For PassMe to work it requires the use of a commercial NDS cart (for authentication) and a GBA Flash cart to hold your DS programs."

While this mod chip will allow you to run pirated games the ability to run old abandonware or homebrew on the DS is enticing.