Was just looking at this cradle in the AC store. It's supposed to charge/sync the phone and charge a spare battery. Look at the phone though, we all know the USB port is on the top of the phone, you aren't going to charge or sync it with the phone right side up like in the pic. You'd have to still plug a cable into the top.
http://store.androidcentral.com/mobi-products-cradle-w-spare-battery-slot/52A143A7685.htm
http://store.androidcentral.com/mobi-products-cradle-w-spare-battery-slot/52A143A7685.htm