Am also a believer of smartphone used as GPS. Pero recently on a very long drive, bumibigay yung celphone due to the heat. Nabilad kasi sa araw sa windshield. Either yung battery overheat alarm goes off or yung gps sensor could not connect until i turn it off for a few minutes. And since im using waze sa provincial road minsan nawalan ng signal while in the middle of recalculating route. Hassle talaga.