Sometime ago I have been stumbled upon a demonstration of Firefox OS. There was said that most applications in Firefox OS are build from HTML5 and Javascript even the more hardware related ones like a battery indicator. Furthermore they pointed out that some of the Firefox OS API become available in Mozilla Firefox browser too. The Battery API is one of those – already available – APIs and it is becoming standardized by the W3C too. This was an inspiration to play around with the that API and build a simple web based battery status indicator relying on HTML5 Canvas, Javascript and the Battery API. You can view the result here.