@kucai: the price is indeed steep if you compare to a phone; if you compare to a professional RTK GPS ($15000) it’s not that bad. :-)

I would say you won’t be able to use a phone, first because it has a really bad antenna and second because you probably won’t get raw GPS data from the hardware. Some models may let you, but I’d guess most won’t. Also I haven’t found any free and working app to actually make something useful even if there was data available.

You can create a base station, costs a bit more, and it will cover about 25-70 km with more or less usable fix quality. StephaneP have linked some webpage for one based on the same F9P chipset.