I have a 3rd-party bit insert for my Leatherman that can check voltage on batteries, so I'm set for this problem (volty by pcpoodle)
Something on-battery would be cool, but with that Duracell PowerCheck implementation never seemed right to me, it seemed to show the battery having more and more power the harder and harder I pushed on the spots. π€·
Not the best, but one I liked that is easy to overlook -- The Mask
Play it with save states though, doesn't have save/continue