Rene Ritchie, in a part of his iOS 8 wants series:

If Apple implemented battery shaming on the iPhone and iPad, then whenever my phone was unusually warm or ithe battery was dropping unusually fast, I could simply open Settings, tap General, tap Usage, scroll down, see exactly which app or apps were causing the problem, and kill them just to watch their power drain die.

Just above this added feature I’d like to see a toggle button for “Show battery percentage when below 20%.” I typically prefer to have the battery percentage hidden, but when my battery is getting low I need to keep a closer eye on its usage. The first thing I do when I get that 20% warning is jump into usage settings and turn on the battery percentage indicator — I wish I had the option to show this information when it’s most important to do so.