A while ago, I saw something like this online. When out in a nature reserve, and photographing animals and birds from your vehicle, one often needs to hold the camera on the window of the car. This mount simply creates a stable platform so that you don't need to hold a heavy lens in your hand. ?

The ball and socket joint allows good movement, and the base fits well on the glass of the window itself.

I've included a multiple versions of both the ball and the base.

The Base

The base comes in 4 versions:

1. A snap fitting ball and socket which, while snug, still allows free movement.
2. A simpler free sliding joint, which does not clip into place. This means that the ball simply rests in the socket without being held (better for rapidly moving your camera in and out of the mount without removing the ball from your camera).
3. A variant of the snap fit with a locking screw 
4. A variant of the free sliding joint with a locking screw

The Ball

The ball comes in 4 versions:

1. A long and short version of a generic mounting system. This option has a center mark in the base for you to drill and press your own threaded piece for your camera system
2. A long and short version, with a threaded hole fitted for the Canon tripod mounting thread

I printed initial versions of this with a 5% infill and it still felt more than strong enough to hold an SLR style camera with a regular lens. I would suggest printing with a higher infill for heavier lenses and cameras

Please enjoy, and give me feedback, comments and suggestions on improvements.