Laser rangefinders have become essential gear, but they have a design flaw. They require that you contort your body to get a clear line of sight to your target. In some cases, that means you have to risk spooking game to get a range reading, showing your head and at least one hand. What if rangefinders had an extended eyepiece with a prism so that you could literally find a range around a corner? I'm thinking of the sort of extension that submarine periscopes use to see from below the water's surface. A periscope rangefinder would allow us to range targets undetected around corners, over obstructions and in tall grass.
Bow Release with Built-In Grunt Tube**
Bowhunters rely on grunt tubes to stop a buck in order to get a standing shot, but in the moment of truth, it can be hard to wrangle a tube, draw your bow and get a sight picture. I'd like to see a bow release with a built-in grunt tube. The release is already right at your face, and it would be a cinch to simply blow on the tube just before releasing the arrow. Design challenge: add a snort/wheeze call to the built-in grunt tube.