Hi-Tech Reviews have published a review of the Eye-Fi Wireless SD Memory Card.

Quote from the review: "Anyone that owns a digital camera knows how boring it can be when you have shot a memory card full of pictures and then you need to stop to find either the USB connector cable or try and find your card reader that you absent-mindedly forgot at brother-in-laws birthday party.
What if you could send your pictures to computer via WiFi, oh you say your camera doesn't support that. I realize most don't, but what if your memory card supported sending pictures over WiFi?"