USB OTG Power Y Cable
This cable can be used with Android devices that don't supply power to the micro USB port, but would otherwise be OTG capable.  The USB A male connector (pictured left) can be connected to a USB power source, thereby supplying power USB female connector (pictured center).  The cable has the following connectors: USB Micro (smartphones / tablets), USB A Female (thumb drives, etc.), USB A Male (for power supply).