The chaps over at Anandtech take a look at the AGEIA PhysX PPU, the dedicated physics processing unit that could relatively revolutionize games as did the graphics processing unit.

excerpt:
At first, we can't expect a new genre of incredibly interactive games. The first few games that adopt the PPU will tack it on like the first few games that embraced hardware 3D. We'll start by seeing effects enhancement (like more particles and objects go flying from explosions or some objects may get an upgrade to being deformable). If AGEIA has it their way, we will start seeing motherboards and notebooks integrating the PPU. If they can get good integration and acceptance of their add-in card, we might start seeing games that require a PPU and are really revolutionary with the level of user interaction allowed. AGEIA really wants to mirror the revolution that occurred with 3dfx, but it may be a better idea for them to separate themselves from that image considering how hard 3dfx fell from power.

Many people don't think a separate add-in PPU will fly. What about vendors dropping both the GPU and PPU on one card? Maybe if the add-in PPU doesn't stick around, we will one day see the birth of a ubiquitous "gaming card" that integrates graphics, physics, and sound onto one add-in board. Or if Intel decides that they need to go the extreme route, we may see integration of very application specific hardware that can handle tasks like physics processing onto the CPU.