One of our hybrid graphics team members has wriiten a dellL702X script to turn on/off the nvidia card from the Dell XPS L702X model using acpi_call.
For more info on acpi_call and its integration into bumblebee, check the launchpad website:
For more information, join the team subscribe to the mailing list at the bottom of the Launchpad page http://launchpad.net/~hybrid-graphics-linux Please join this team if you are new by clicking on the "Join Team" link at the right of the Launchpad page. It's important to have as many users in the community as possible to request for appropriate support.