The WiFi uploading Eye-Fi SD card made a big splash when it was first introduced, but now Eye-Fi has a whole line of different products. The top of the line is the Eye-Fi Explore, which supports geotagging without using a GPS. Instead of GPS hardware, it uses the Skyhook Wireless Wi-Fi Postitioning System, which correlates the position of the Eye-Fi’s access point to GPS locations, creating virtual GPS functionality. This allows photos taken with the Eye-Fi to be be geotagged. Of course, the accuracy of the system is noticeably lower than true GPS and seems to be affected by a number of external factors, but it is still accurate enough to tag the photo within the immediate vicinity of where it was taken.
WiFi positioning is great feature, but certainly not limited to photography. Since the Eye-Fi is at its core SD storage media, you could probably have it geotag data saved to the card, even if it wasn’t created by a digital camera..