In the latest Issue of EDGE (166), they have an 8 page article about the making of Dreamcast classic by Bizarre Creations, Metroplis Street Racer (the fore father of Project Gotham Racer). A great read, and I recommend to any Dreamcast fan ( and MSR or PGR fan) to get it.
But one of the side articles shows a picture of Geometry Wars running on the VMU! Could this be the Holy Grail of unreleased games? Well no, it was just an animation by Bizarre Creations animator Jeff lewis.