We live in a world of battery chargers and AC adapters (which are also quite often battery chargers). And the main problem with these power bricks, wall warts, and easy-to-lose pocket chargers is that they don't know when to stop.
When the device attached to them needs power, they provide it. When the device is entirely charged or turned off, they still give it juice, although not as much. And even when the device is removed, the plugged-in adapter or charger continues to draw a bit of electricity. Keep enough of these vampires plugged into wall sockets 24/7, and the amount you waste can add up.
A smart charger knows when it's needed and shuts down when it isn't.
Since it's impossible to create a smart charger that can support countless numbers of devices (each of which came with its own unique AC adapter), they tend to support the two most common standards: USB and the iPod/iPhone connector. Of course, since you can charge an iPod or iPhone from a USB port, only one standard really needs to be supported.
But iPods, iPhones, and USB-chargeable devices are not really the problem. They're already at least somewhat smart about power. I tested four USB-chargeable devices--a Samsung Omnia smartphone, an iPod Classic, a Creative Zen MP3 player, and a Samsung YP-Q2 MP3 player--without a smart charger, to see how much they waste after a charge is complete. With all four, the trickles (if there were any) were so small that my Watts Up Pro said they were using no power at all.
I can't tell you with absolute certainty that the smart chargers I looked at can accurately cut your power usage. I can say, however, that if you don't keep multiple chargers plugged in round the clock, they won't save you much.
I looked at three chargers--Belkin's Conserve Valet, and the iPod and mini-USB versions of the Ventev EcoCharge--although two of them were essentially identical.
Whether it saves power or not, the $17 Ventev EcoCharge makes a handy little portable charger. It fits easily in the palm of your hand, and plugs into an outlet without crowding other devices. The 62-inch cord ends in a mini-USB, micro-USB, or iPod connector, depending on the model you buy. An LED light tells you when it's finished charging.
The device also has a hidden USB port, which allows you to power any USB-chargeable device in addition to the one you bought the charger for.
The $40 Belkin Conserve Valet (not yet available as I write this) takes a different approach. It's a station, basically a 9-by-6-inch platform with four USB ports. You plug cables into the ports (the plugs can be standard USB on both sides, or special ones like USB iPod connectors), wind excess cable around the Valet's inside, and plug the Valet into a wall socket.
When you want to charge something, you plug it into the appropriate USB cable and then press the Valet's on button. When the LED light stops glowing, your device is charged. It's a convenient way to charge your devices, assuming you charge them only in one particular location.
These surge protectors and chargers can help you cut your power bill, but don't expect miracles. In fact, conventional surge protectors, placed where you can easily reach the power switch, will save you even more--provided that you cultivate a few good habits.