Western Digital have a new product available
The WD My Passport Wireless Wi-Fi mobile storage.
It has a long lasting rechargeable battery, and includes an SD card slot. So you can the device out with you when you shoot and backup your photos by taking the SD card out of you camera, putting it into the slot on the case of the hard-drive and copy all your photos onto the hard-drive, while on the go. The 2tb version sells for around $390.00
Great idea for us photographers!