Craft Measure gives you a bundle of the measuring tools
knitters, crocheters, and weavers usually have somewhere around the house that is as easy
(or hard) to find as your phone. Its tools include:
A short ruler (long enough to measure ribbing on typical cuffs).
A visual sizer for knitting needles (you visually compare the tool's image of a given size against your needle)
A visual sizer for crochet hooks
A visual sizer for loom reed (dents/inch).
A visual sizer for small gauge squares (enough to decide your gauge is close enough to warrant a full size square, properly measured).
Craft Measure version 1.0 has been available for $0.99 US since March 2012.
Craft Measure 1.0 has a trial mode. In trial mode, the one limitation is that you will have to do the initial calibration every time you
start Craft Measure. That means that you will have to have a ruler handy to do calibration before you use any of the tools. You
can use the (free!) trial mode of Craft Measure to see if you find the tools usable and useful.
Craft Measure 1.1 is coming in September 2016. It will be a free application with no ads.