Well the Eye-Fi card arrived today. Setup was easy enough though not a straightforward as I'd expected. After a bit of fiddling, my D5100 photos are being transmitted to my iPad. My wifi router is in my study. There, the photo transmits almost instantaneously. From my lounge, about 60 ft through two partition walls, it's taking 10 - 20 seconds...which surprised me since my iPad, iPhone, iTouch and laptop (phew) don't seem to have any lag. I wonder if that's down to low power consumption of the card?
Anyway, seems to do what it says on the tin...so I'm off to play now