A note on USB charging sockets. The USB has 4 pins 1 & 4 are charging pins and 2&3 are data pins. The resistance or the voltage on these pins are read by the device to determine if it will use it to charge and how much.
The "Chinese" standard is for these data pins to be shorted together or 0 ohms. The device will (if compatible) will draw 1 amp charging.
The same "standard" is 200 ohms (essentially shorted) also draws 1 amp.
The tablets and Apples look for something a little different.
Apple has been working to keep their experience pure for their customers ( this really means more $$ for Apple).
Nowadays the iPhone expects a certain voltage on those two pins to decide how much current to absorb from the charger. Putting a 2.0 V voltage on both the pins the iPhone will absorb about 500 mA, while with 2.8 V on D- and 2.0 V on D+ it will absorb about 1000 mA.
There are different setups for different devices so it is likely that a generic charging port may not work with all of your devices. There are some ports that are switchable that will work with 1 amp, 2.1 amp (or 2.8) both apples and other devices.
Here is one, but no charging specifications other than 2.1 and 1 amp
Unfortunately it is difficult to a 12 volt multi device charging system.