The Canon WFT-E4A Wireless File Transmitter allows you to wirelessly transfer your files from the EOS 5D Mark II to a secure network. In addition, it also serves as a vertical grip, duplicating basic camera controls for easier vertical shooting.
The WFT-E4A can transfer images wirelessly through either 802.11b or g protocols, and has a USB connection for situations where wireless access is limited, or impractical.
It is also equipped with a powerful antenna, capable of transmission up to 150 feet. The Wireless File Transmitter can connect to a third-party GPS device via the USB connection, providing the ability to attach GPS information directly into the image's EXIF data, or you can plug a compatible USB 2.0 hard drive into the transmitter's USB port, and actually shoot directly to a large portable hard drive.
The WFT-E4A is powered by the LP-E6 lithium-ion battery, which does not supply any power to the camera itself. It also allows you to check the remaining capacity on the camera's power source info screen.