Get an Android based phone/tablet, do offline maps and you’re good to go. As long as the GPS chip is working you’re good to go. You don’t need a SIM as long as you can follow a map. It won’t give you turn-by-turn direction but you won’t be lost in a city. I just used that solution in Istanbul.
Your original question was keeping track of your partner, so that threw everyone off (well, it threw me off).