Which GPS do you recommend?
Firstly, get the Wifi+Cellular (3G/4G) iPad which has an inbuilt GPS. This works fine for most people. If you have any problems, or have a WiFi-only iPad, try one of the following:
The plug-in Bad ELF GPS will enable GPS on your WiFi-only iPad or 3G iPad if you are forced to work in Airplane mode (which disables the onboard GPS). You can get them for around $99.
The Bad ELF GPS Pro is a great device that allows multiple iPads to use a single receiver. Also doubles as a data logger.
The Dual Bluetooth GPS has also been reported as being very good by some customers.
Gamin GLO GPS+GLONASS device that works very well too.
This list isn’t comprehensive, and is based on customer feedback. Technically, any GPS that says it supports iOS should work with OzRunways.