Leviton has recently introduced a new in-wall USB charger to help simplify things. Even though other in-wall USB chargers are on the market, the Leviton T5630 uses a standard Decora/Designer form-factor, which makes it compatible with a wide variety of wall plates, and can be used in multiple-gang installations (such as having it installed next to a light switch).
The two USB ports on the Leviton T5630 are designed for use with different devices, depending on their power draw. The USB port on the left will output up to 0.7A, while the USB port on the right is capable of up to 2.1A. The right port also incorporates an auto-sensing chip, which will properly adjust the amps depending on the device connected.
For example, if you have two phones, you can connect one to each port, or a phone to the left port and a tablet to the right port. But you cannot connect two tablets to both USB ports at the same time, since that exceeds the combined maximum capacity of the USB charging ports. In that case, you would have to use a standard wall-charger for the 2nd tablet and plug it into the bottom AC plug.
The Leviton in-wall USB charger comes in White (T5630-W) and Light Almond (T5630-T) and is currently available for purchase at Amazon for $21 and $26.
source: Leviton (and video demo)