Regarding the Bad Elf, I agree with a64pilot. I had an earlier version of the plug-in type Bad Elf and used it with a Wi-Fi iPad
2, but it always felt a bit cumbersome and made the iPad
harder to handle. Had to take care not to bump the Bad Elf, the iPad wouldn't fit into the waterproof pouch any more, and charging
while using the GPS
was possible but fiddly because one has to use the (short) mini-USB cable supplied with the Bad Elf. As for performance, the GPS
worked fine with navigation
apps, but getting an initial fix seemed quite slow and sometimes required unplugging the unit and plugging it back in to get it going. When I upgraded my iPad, I got a 3G model with the internal GPS chip, and never looked back...