This is an Android app and widget that I created for my partner that reads from a Google Drive Spreadsheet, does a bit of math on the data, and displays some values (recent, min, and max temperatures -- which are written by a Raspberry Pi hooked to a temperature and humidity sensor).
I hacked this together quite quickly, and it's far from production code, but it might be useful for someone who is doing something similar. There are too many shortcuts and to-dos to bother listing, but it basically works.
Feel free to create an issue if you have questions or whatever.