Back in the old days, used this to build a DRO for the z-axis of a milling machine: <a href="http://www.nerdkits.com/videos/digital_calipers_dro/" rel="nofollow">http://www.nerdkits.com/videos/digital_calipers_dro/</a><p>And then got contacted by a blind mechanical engineering student who asked if we could make a set of talking (text-to-speech) digital calipers, which we did: <a href="http://www.nerdkits.com/videos/talking_calipers/" rel="nofollow">http://www.nerdkits.com/videos/talking_calipers/</a>