Palm Pre does it, using the Touchstone. Now iPhone and iPod Touch can do it too, thanks to WildCharge.
Wire-free charging technology integrated into a flexible protective cover that fits snugly over the body of your iPhone. Compatible with all models, including the new 3GS.
So basically, if you’ve lost your iPhone/iPod charger cable (again!), simply put your iPhone on the charge pad and it will charge it for you, without having to plug in any cables. Only downside is, so far, you will need to use the Wildcharger skin for your iPhone, which also acts like a protective case, so it’s not all bad.