How I Use It
I typically use GeoGuessr in my class as an enrichment activity that students can complete if they are finished with other work. Some locations have very few clues to help students accurately guess the location so they have to think a little deeper about the visuals that are present - language of the street signs, type of vehicles (direction in which they are driving or which side of the vehicle has the steering wheel), kinds of homes, etc. Sometimes I have students write their scores on the whiteboard in the front of the room to see who has the highest score for the day.
I think it is a fun enrichment tool. It would be difficult to make it a specific portion of the curriculum but they do enjoy playing it. If you want to expand a little and create your own game in a similar format check out GeoSettr - http://geosettr.com/ This site allows you to create locations for your own version of GeoGuessr which you can then share with others. This is one way in which you can make a GeoGuessr game that has specific content to your own curriculum.