We already know all about NVIDIA's Optimus technology. The tech changes between a discrete GPU and integrated GPU in netbooks and notebooks automatically. It is a big part of the next-generation ION platform for portable machines.
Optimus has shown up on video giving a better idea of the video switching prowess of the technology in the real world. NVIDIA set the demo up with a LED grafted onto the discrete card to the discrete GPU so you can see when the thing is powered up.
NVIDIA even went so far as to pull the discrete GPU from the test system entirely when not in use and the machine goes on as if nothing has happened. This shows off that the GPU is shut off electrically saving power during idle. Cool video for sure.