Sprav, a gizmo shaped like a water drop, wants to save you from being a hot-water-hogging shower jerk. It clips onto the pipe behind your shower head, listens to the water flowing through the pipe, measures the temperature of the water, and lets you know when you’ve spent way, way too long zoning out in there and are about to turn into a prune-fingered, energy-wasting disaster.

The guys behind this invention are three fresh-faced Case Western students who are pitching this as way to save money on your water and heating bill, with the added side benefit of doing a little bit to decrease carbon emissions. Using a phone app, you can set it up to start glaring at you — there’s a little light at the top of the drop that turns green, yellow, or red — when you’ve used too much energy.

It’s a neat, simple way to fight back your worst instincts to just sit in the shower and let the hot, hot water rush around you. There’s just one design flaw that we can find: You can always avoid looking at it, just like you avoid the insistent door knocking and your roommate’s shouts of “save some hot water for the rest of us, you dick!”

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