Most of us uses our phones to navigate. You can start a trip anywhere, including in remote areas, with a portable navigation system, portable GPS, etc. A smartphone needs a cellular signal to plan a trip and download map information; a portable GPS has maps built-in.  Besides, a display in the portable GPS is wider than most phones, with a diagonal of up to 7 inches. If your car doesn't have Bluetooth, the GPS device's microphone and speakers can be used to make calls hands-free.