The Idea is Good

I found an Android app called Rangefinder.  I was wondering how something with only one eye would do range finding.   It is a clever hack.  It puts up a silhouette of a man, a deer, an F-150 truck among other choices.   You pinch or expand the silhouette until it matches the size of what need the range and when they match you get the distance in feet and inches.  I would do a few things differently: instead of arbitrary objects I would have put out a 1 meter or perhaps 1 foot ruler to make it not specific to any particular target.  I would also have included a zoom feature; anything more than a few hundred meters away is a couple pixels.  A 10x or 20x "scope" option would make this more useful.

A little more investigation finds it has a metric mode.  The F150 is roughly 2 meters high so this takes care of my first concern.   There is also a ghost mode that makes the silhouettes red or green.