Batteroo Batteriser, $2.50

batteriser

The Batteriser battery sleeve promises to extend the life of your batteries up to eight times longer by drawing out their remaining power -- which you were about to throw in the garbage. (When disposable AAs stop working, they actually still have about 80% of their power remaining.) The tiny, 0.1 millimeter-thick stainless steel Batteriser sleeve features an incredibly small circuit board, built to tap into the battery's remaining energy.

First published December 22, 2015: 2:55 PM ET