If you want to measure things on the go, the fact that your smartphone has a set pixels per unit length makes the screen an excellent ruler. Unfortunately, most of the options in the Play Store resort to silly skeuomorphism, are paid, have ads, or are far oversized for their function.
Except for Ruler, which is the exact opposite of all the above. It supports inches and centimeters, has dual axis software caliper jaws, and comes calibrated right out of the box for popular devices, including the Samsung Galaxy S5. At 699 KB, it won’t take up much space on your phone either.
The only thing Ruler’s missing is a dark theme for AMOLED screens and the ability to be installed to the SD card. Try it out!
Also, Android level apps are useless because most Android phones can’t be laid flat on any side other than the one the screen’s on.