Oooh this is a cool concept. Integrating the battery info of peripherals. This reminds me of this idea I once had to integrate the reception of your phone when using it tethered as your internet source, and showing it as the wireless strength, instead of just using th icon of a ethernet connection. Perhaps something for when there is Android/iOS integration with elementary.
Further I quite agree with the common comments made below.
Perhaps something more like your Indicator Sound at [link] where you have mono color icons that are more simple as well as the volume bar would be modified for the charge level instead and perhaps the color would turn from gray to red if it's under say 10%?
I like it. It'd be cool to see the battery status of connected devices.
One feature I'd love to see would be smarter battery life estimation. Ever unplug a laptop, then click the battery icon and see that it'll last for nine hours? Then you wait for five minutes and check again, it's 4.5 hours? I know for a fact that my laptop's battery lasts 2.5 hours, and if the indicator would simply remember how long the battery typically lasted, the estimations would stop being so useless.
Also, how about different power modes? Power Saver, Normal, Performance? Power saver might have a lower screen brightness, lower cpu scaling and less idle time before the screen turns off. Normal would be... normal. Performance might have higher cpu scaling. There are a number of power saving and performance increasing options that are usually only accessible via the command line, it'd be nice to have a graphical interface for them.