Every professional photographer has experienced the problem of keeping up with multiple lenses and having to switch them out quickly as needed.  Swedish startup Frii Designs has developed a belt-worn holster made of steel & fiber-reinforced nylon that allows you to carry 3 lenses at once.

The TriLens Holster ($98) mounts the lenses in a triangular pattern that rotates 360 degrees around a common center.  In this configuration, the heaviest lens will hang to the bottom while the open lens mount is accessible on the top.  There is a built-in stabilization system that helps prevent excess bumping.  The lenses are held securely enough you can even do backflips without losing one.

The holster is heavy-duty enough that it can support up to 100 kilograms (220 lbs!) to handle whatever size lens you need.  Compatible with Sony, Nikon, and Canon lenses and comes with magnets for attaching the lens cap to the open mount, thus preventing dust, dirt, or water from getting into the empty slot.   Details in the video.