Imagine if your smartphone was as advanced as your toothbrush -- at least in the charging department. That would be cooler than your peppermint toothpaste.

If you've got one of those high-end vibrating toothbrushes or any of several waterproof electric shavers, then you already own a device capable of a neat trick called wireless charging.

When you put that toothbrush in its charging cradle, you'll notice that no metal contacts are exposed for the electricity to charge the batteries. The toothbrush charges magically, right through the plastic.

Don't look now, but that very same technology is coming soon to your cell phone, your iPod, even your laptop. 2007 is the year that truly mainstream wirelessly charging products finally go on sale.

How it works

There are three basic technologies for wireless charging: radio, resonance, and induction.

Radio charging is well suited for charging low-power devices at long distances -- some 30 feet away. This technology is ideal for trickle-charging advance RFID chips affixed to, say, palettes loaded with products in a warehouse.

Resonance charging makes sense for robots, cars, vacuum cleaners, and other applications that require massive power over minute distances -- essentially making contact with plastic, but not metal.

Toothbrushes now, and random gadgets will very soon, use inductive charging. This technology uses a coil to create an electromagnetic field across a charging station surface. The device then converts power from the field back into usable electricity, which is put to work charging the battery.

(Meanwhile, researchers at MIT said this week that they have come up with a way to wirelessly supply power that could lead to the development of gadgets that don't require batteries at all.)

Where wireless charging gadgets come from

Wireless charging gadgets will come from some well-known companies, including Apple and just about every cell phone handset maker, as well as small startups you may not have heard of.

An Apple patent submitted in 2005 and published in February describes technology for charging an iPhone or an iPod using zero-contact induction for not only charging but data transfer -- an arrangement that requires inductive coils in both base station and device. Apple's patent covers both single coil (charging only) and two-coil (both data and charging) approaches.

Optimists speculate that Apple's inductive data-transfer technology might be used for synching, say, songs on an iPod or an iPhone. But pessimists, including Yours Truly, fear the main purpose might be locking out non-Apple products from getting in on the easy charging or preventing users from charging Apple devices on non-Apple chargers. Apple devices may need to give the secret handshake before Apple chargers give up the juice.