Very handy and works great!

Tried it out today using my iPad and iPhone. Works very well. Obviously (and its very clearly stated in the app description) it isnt guaranteed to give you extremely precise measurements, but I checked the measurements I received against a tape measure and all were within 1/8" - 1/2" I did make sure to set them temp. to my current location. I managed to get it while it was free but I think $1.99 is a fair price.
I feel the need to comment on those who are complaining, having purchases the app before reading the app description, or simply following the calibration instructions. Why!? MOTHER OF SOBBING CHRIST... Why do people give apps terrible reviews when they have clearly purchased the app without reading about any limitations or instructions the app description has for them to freely read before purchase? I understand if the app seller hides these things, but not when theyre clearly stated. Its unfortunate.

FrankWit.com about Acoustic Ruler Pro