Paul K Canavan When describing anything to someone who is blind, use a clear word image. Color, texture, form, and landmarks are all examples of features to include. DO address them by touching their arm or using their name. This communicates to them that you are speaking to them and not to everyone else in the room.

I hope something useful is here https://trepo.tuni.fi/bitstream/handle/10024/65485/B-2005-2.pdf?sequence=1&isAllowed=y

you can try google "TongueTouch Keypad"

"An Isometric Tongue Pointing Device"

"Tongue Display Project"

Thank you !