Another option would be something like a wireless file transmitter as Canon offers for the EOS-1Ds Mark II, the 1D Mark II and the 20D.
The name of it is WTF-E1
"The Wireless File Transmitter is designed to enable photographers to transfer their images from their camera through a wireless network to a computer, whilst not interfering with the process of taking pictures.
The key advantage is to provide a faster workflow for professional photographers, allowing them to concentrate on the process of picture taking while the transfer happens automatically in the background."
I read in a german forum, it works well.
It costs about 1'000 Euro.
http://www.powertext.ch Canon 20D / Sigma 8mm / Roundshot VR-Drive