I have created a unique and a very useful portable magnetic keyholder product : Portmag keyholder. This product can be used on a mortise plate of a door and / or a fridge. I have even used Portmag on my metal clothes horse as you can see in the photo above. You can see the mortise plate application in the top photo.
Here is a quick video from Youtube channel. It shows the Portmag fridge application in action.
Here is a demo of the Portmag keyholder mortise plate of a door demo. It's from my Youtube channel.