An older neighbor of mine from 35 years ago told me the greatest invention he saw was the furnace thermostat. It really got me thinking about things I took for granted, having always woken up to a consistently warm house. Of course in my lifetime it wasn't until my teen years that our house got A/C, that we'd only run during the most hottest weeks of the summer. Now I run it summer long, mostly to keep pollen out (although I don't recall people talking about allergies in my youth), and I would never consider a South Carolina beach vacation in July or August without it.
Having navigated Paris, with it's one way streets, using only printed mapquest directions, still a step above maps, I greatly appreciate GPS when driving in foreign countries. The combination of being in unfamiliar locations as well as trying to match street signage names in a foreign language created frequent stops to reorient and to reset my stress levels. GPS is a game changer when driving in a foreign country - especially in Greece where the cyrillic alphabet also comes into play.