Not a bad idea for sockets.
I just came up with something for bits that does technically work, but I'd have to modify a whole set of bits.
All I did was put a bit in my vice and hammer a lip onto the back with a ball peen hammer, not it can drop in without falling through.
Of course you have to keep your finger on the back, but it does work.
This would be a great simple solution if I could work for a 1/4 hex-square bit.
I'll keep trying to see if I can come up with a better solution for bits.