Your chances of having the first one on the block: Moderate, given the publicity the Explore and its 4GB cousins the Home and Anniversary Editions have received.
What you must know: Of the three Eye-Fi models, the Explore is the only one with upload-to-Web and bundled hotspot access service included.
What you need: A digital camera with an SD card slot (or SDHC for the Anniversary Edition). The Explore and Anniversary Edition cost $130 each, while the Home edition costs $80.