The Tactile Caliper is a low-cost measuring ruler for people who are blind or visually impaired. Developed by SQUIRREL DEVICES (past winner of the Louis Braille Touch of Genius Award), the Caliper allows its user to measure with accuracy and speed. It displays readings directly in braille to 1/16th of an inch. It is a simple mechanical instrument that can be used anywhere by people of all ages.
Available from National Braille Press: http://www.nbp.org/ic/nbp/CALIPER.html