It can turn on/off your discrete GPU for compute without graphics, without running the program with optirun. It also does not start another X server, like optirun does. It is ideal if you want to use your GPU only for CUDA compute.
You need to have bumblebee installed in order for this to work. For more details on how to set it up, see https://wiki.archlinux.org/index.php/bumblebee.
Copy the file "gpu" in your path and change it's permission with chmod +x.
To turn on Nvidia GPU, use:
gpu on
To trun it off, run:
gpu off
Note: you can only turn it off if nothing is using it.
To see whether the GPU is on or off, run the tool without arguments:
gpu