OMFG!!! People... READ!!! All questions can be answered by reading... http://www.ageia.com/
There will be only two card makers offering them:
BFG & ASUS (Currently).
They will be in PCI-express 1X/4X & PCI flavors: (Haven't heard anything about PCI-express 16x, although it would be nice with an extra PCI-e slot on an SLI board.
Major Software Dev. companies whom use the "Ageia Physx SDK" and integrate it into their software will support the PPU card. This also includes 3D rendering and design appz, not just games.
Games using the Unreal Engine 3 (Currently to name a few, EPIC, ATARI, Buena Vista Games, NCSoft, Gearbox Software, Hi-Res Studios, 10Tacle Studios, Sony, Vivendi, Namco, MICROSOFT, Midway, Timegate Studios, America's Army...) Just to name a few...
So save your pennies kiddies cause if you don't have a PPU... your gonna get owned...