I've been looking for an app like I'm about to describe below, but I can't seem to find it. I would make one myself, if only I were good at Android programming. So, instead, I'll put the concept here and see if somebody with the resources could turn it into an actual app.

It's a live wallpaper, capable of transforming according to the battery. It won't be a simple image of a battery or a container with a liquid (or any other content, for that matter) that represents the battery remaining. Rather, it would be a fully-fledged, aesthetic HD wallpaper image (perhaps a gradient, or a pattern, or an abstract image) that's bright at first, then grows darker / heavier in color as the battery drains.

If you're interested, I'll appreciate it if you let me know. Also, feel free to take all the credits about the app.

Or, if you find an app that seems like matching my concept above, please let me know and post the link.
Thank you.