I've experienced the 3D virtual reality googles Oculus Rift now for 4 weeks and had one particular problem:
How can I find the correct key that I need on my keyboard when I don't see anything?
So I came up with a cheap €12 USB numerical pad and some on-top keys which have clear differences in haptics and feelings.
I simply glued those onto the numpad and voilá here is my low-cost Oculus Rift tactile keyboard. Simply configurated the most common commands to the respective keys and practiced a bit.
Works great for me! :-)
Simply use glue to attach the tops onto the different keys, preferrable try to place similar icons away from each other.