I did this keyholder initially as a birthday present for a friend, but I really liked the design so I ended up making one for myself. The design is based on a magnetic connection between a small magnet hidden behind the wall-mounted plate and a steel ball attached to a triangiular acrylic keychain. The design works with very basic geometries, and I wanted to enhance the mysterious nature of the magnetic connection in the expression of the holder.
I experimented with some variations of the textures of the acrylic, leaving one plate smooth and glossy, and another "brushed" or "frosted". I personally prefere the latter as it is more smudge-resistant and has more "character".
The space between the acrylic plate and the wall is intended to give the holder a more light or floating look, but also works for hangin headphones (another item I used to constantly misplace).
If anyone is interested, I'll be glad to make an instructable for this :) just let me know in the comments