Keson Compact Measuring Wheel

You roll the wheel along the ground, and it counts how far it's gone. That's pretty much it. No batteries, no fancy features, nothing special (which means I'll probably break down and buy a cooler one at some point). It can count up to ten thousand feet (a little under two miles), and it marks inches pretty well too. If you roll the wheel backwards, it counts backwards, which could be handy. Press the button to the left of the counter to reset it.

As you can see in the photo below, this "compact" measuring wheel can telescope out to a nice length, reaching from the floor to about waist height. Just untwist the segments (counterclockwise), pull apart, and tighten (clockwise). I haven't had much of a chance to use it yet, but hopefully I will someday.