The retracted springs take up a ridiculous amount space in the phone's case; don't expect this in your device any time soon. (By which I mean: ever). A version for laptops could be fantastic.

The shock absorption capacity is greater than necessary; experience shows that a simple silicone bumper is effective. The device can take a certain number of G's; it's not exactly an egg. A bumper also reduces drop incidents by providing grip. (Aluminum cases can dent through a bumper, though.)

A simple through hole or other means of strap attachment allowing a phone to be put on a string takes less space. "Bungee cord for your phone!" Cameras have strap attachments; it didn't catch on for phones due to the obsession with smooth design, perhaps.