A magnetic Gopro mount can be really useful for a lot of footage, as for exemple car footage. I propose a DIY to make it almost for free and in two minutes. The hardest part is to find a magnet strong enough to support the Gopro's weight
Step 1: What you need and assembly
You will need a old hard drive and a Gopro pad.
First open the hard drive and remove all the component. You will see the discs and the reading head. To sweep the reading head above the disk the hard drive uses the Lorentz force. That means that you need a electric current (actuators) and a strong magnetic field so strong magnets (see picture). In a hard drive you will get two magnets.
Once you get the magnet, clean it and glue the Gopro pad on the opposite side of the magnet.
You are done.
if you need it, you can add some rubber pad to avoid the Gopro to rotate.