Martin Juhl has been relentlessly working on bumblebee and he just started working on automatic switching support for Ubuntu, while work is also being done to support other distributions.
The idea is to have the nvidia card always switched off and automatically switch it on when a program is executed using optirun. Once the program finishes, the card will automatically switch off again. The current implementation uses acpi_call, so only laptop models supported in acpi_call will have this feature working, at least for a while.
For more information:
PD: Martin's Bumblebee Project open source efforts are being fuelled by RedBull, find his donations account below if you want to buy him more: