Very intriguing app

This is really a well done app. The interface may not be the slickest, but it does exactly what it sets out to do. For those having trouble, consider a few things:
1)Sound reflects best off of hard flat surfaces, so trying to measure a distance to something absorptive or irregularly shaped may not work well.
2) Setting the air temperature will indeed affect your measurements.
3) Cupping your hand under the microphone and speaker as shown in the video will increase the volume of the clicks by focusing the sound from the phone; think of your hand as a crude megaphone or acoustic horn. This increases the signal to noise ratio and will increase the accuracy of the app.
4) Consider the ambient noise in the room. If you are trying to measure in a noisy environment, your signal to noise ratio will be poor and results will be inaccurate.

In closing I really am impressed with this; I would not have thought that the built in mic had the sensitivity to detect reflections from those distances. Well done.

Echols85 about Sonar Ruler