The Eye-Fi adapter for digital cameras is edging closer to release: Eye-Fi has developed a Secure Digital (SD) card with what will probably be 2 GB of storage and a Wi-Fi radio in it that work in almost any camera that supports SD. The likely sales price is $100, according to this News.com article. News.com and other publications published stories yesterday and today triggered by the announcement of a $5.5m investment in the firm from venture capital firms.
I have not yet seen an Eye-Fi card, but my expectation is that they have managed to hijack the process by which cameras can print to a USB printing, with the Eye-Fi simulating a printer for the purposes of transmitting an image. Or they may have a set of triggers or default behavior that causes the Wi-Fi radio to transmit images when stored in a special folder (supported by some cameras) or just on the card at all.
Eye-Fi requires configuration of their card through special software. And because the camera's don't require any direct support of the Eye-Fi device, you won't be able initially to configure to any arbitrary network. It's a perfect match for Devicescape, where an Eye-Fi user could maintain network profiles on Devicescape's servers and obviate any configuration whatsoever.