The Canon WFT-E3 Wireless File Transmitter is a more than valuable accessory for your EOS 40D. Designed not only for people who are spur-of-the-moment, "on-the-go" shooters such as news or sports photographers, this unit allows wireless transfer of files for anyone who wants to rapidly "dump" their images for safe keeping.
For added flexibility, the unit can be connected to an external USB storage unit or via the unit's USB port, plug in a compatible USB hard drive - thus allowing direct shooting.
The unit is also designed to be a vertical grip adding additional versatility. Finally, remote control is also possible as well as image viewing using the unit' s built-in web server.
Note: When used as a vertical grip, a separate BP-511A battery is required