Wireless SD cards are a smart product for forgetful/lazy/busy people. Toshiba's new FlashAir card is the first which allows you to transfer data both to and from the card -- an idea that's got a lot of potential.
Eye-Fi's wireless cards are awesome. They allow you to automatically beam photos to your computer over Wi-Fi, and in the absence of a wireless network, to blast them directly to any device that can connect to Wi-Fi. Toshiba's FlashAir card does the same, but can both send and receive data wirelessly. If the technology catches on and there are two compliant devices -- cameras for example -- in range, they'll be able to exchange data as well.
The FlashAir is a logical evolution of wireless SD. The question is what exactly would you use it for? Toshiba clearly envisions people sharing photos between cameras, but that's actually not the best idea. Pro photographers will tell you that shooting photos with multiple cameras on one card can lead to corrupt files. Wireless hard drives already exist. Perhaps these cards could be useful as more tablets with expandable memory are released. We've got some time to figure it out: Toshiba has only demoed a 8GB version, pricing and availability are TBA. [Toshiba]