Keeping your gadgets charged can be a real chore, especially if they all require you to lug around different cables and wall adaptors. That's even the best-case scenario, where you have the time to wait and leave your device plugged in while it draws power from a wall outlet. When you have to keep on the go, your options rapidly diminish. Sure, there are solar chargers available that can interface with most gear, but then you're limited to being outside and at the mercy of cloudy weather. They might be good for a camping trip, but can suffer in the sun-blocking urban valleys of cities full of skyscrapers. RCA's Airnergy is a fascinating new charging solution that debuted at the CES, able to extract useful amounts of electricity from ambient WiFi signals.

All radio waves are energetic. You might have built a crystal radio as a kid, where coils of wire can pick up an AM signal and play it through an earpiece without needing any battery at all. RCA is taking advantage of the ubiquitous nature of microwave-band WiFi signals that pervade urban environments. The Airnergy just sits there and passively soaks up that energy from any nearby WiFi devices.

A phone-sized Airnergy charger will be available this summer for around $40, and will let you charge devices that use USB for power. The demo unit at the CES was able to charge a BlackBerry in under two hours, but the CES is practically flooded with WiFi signals, so your results may take longer. The charger has its own battery inside, so it can store up power to let you charge your gear even when there's no WiFi in the vicinity. The same tech should make its way into an integrated battery later in the year. Swap your phone's old battery with an Airnergy model, and you might never have to worry about charging your phone again. We'll be keeping an eye out for some real-world tests, as this promises to be a really exciting idea.

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