This app was mentioned in 5 comments, with an average of 2.20 upvotes
Shameless plug: Market Fanatic shows you farmers markets in your area, and you can view them in a map format.
There's an app for that, Market Fanatic
Market Fanatic. Admittedly the use (finding farmers markets) isn't very common, but it's definitely material design and open source.
Market Fanatic. All I really did was request permission for location functions.