Android: It's easy enough to glance at your phone and see where your battery level is at. However, if you want another fun, handy option, check out Energy Bar. It's a free app that turns your phone's status bar into a battery indicator.
Energy Bar is just another neat way to visualise your phone's charge. It basically turns your status bar green when your phone is charged, and as your charge wears off, the green bar shrinks. Once you download the app, you have to grant it permission from within your phone's settings, and then you can customise the bar to your liking.
For example, you can adjust the thickness of the bar anywhere between 1 and 21 pixels, as GadgetHacks explains in this video. There are some additional effects that are only available on the paid version ($2.61), but the basic free version still offers quite a few customisation options, too. Check it out for yourself at the link below.
Energy Bar [Google Play]