I have a iPad1 3G I don't have a subscription ,I just plugged in the 02 sim card supplied when I bought it
I bought a RAM mount off eBay and use it in my heli it's never lost signal yet
I've even used it in a 737 as a passenger at 35,000 ft but you have to hold it next to the window it worked very good
Only drawback i can see is using it in bright sunlight and glare it will need to be placed where you can see it