Whilst not strictly a woodworking product, sometimes a micrometer would nonetheless be handy to have in a woodworking shop.
A micrometer incorporates a calibrated screw for making precise measurement of components in mechanical engineering and machining as well as most mechanical trades, so would be great for measuring extremely fine tolerances in woodworking and on machinery. The spindle is a very accurately machined screw and the object to be measured is placed between the spindle and the anvil. The spindle is moved by turning the ratchet knob until the measured object lightly touches both the spindle and the anvil.
This iGaging unit has a large 35 x 16mm digital readout that will show metric, decimalized and fractional imperial measurements across a 0 - 25.4mm range. It is accurate down to 0.00127mm/0.00005in with a spindle lock placed for easy use next to readout. Great quality and accuracy for any application.