Windows: PwrDrain is a Windows Sidebar gadget that can show you which applications or activities are the most power intensive. It's also a neat-looking power meter.
Photo by Hillwalker
Most power meters show you the remaining battery charge, but PwrDrain shows you the power consumption in real time. Switching from an energy-saving battery mode to a high performance one, for example, will make the needle gauge move. This can tell you at a glance what's eating into your battery life.
Like other gadgets, you can place PwrDrain wherever you want on the desktop and it even comes in a different, though still old-fashioned style if you prefer (though in my tests, that squarer gauge wasn't responding).