With iOS 8.2 and earlier, Airplane mode in iOS would turn off all four radios in an iPhone: Bluetooth, Cellular, GPS and Wi-Fi. Starting in iOS 8.3, that changed with GPS. Plus, starting with iPhone 6, NFC is not disabled either.
Apple reportedly has plans to introduce new Apple Watch models this fall with a GPS and barometer. The new features will be packed into a design that looks essentially the same as the original Apple Watch to accommodate a larger battery.