Smart home Sensor dashboard for Temperature/Humidity monitoring

You know the problem: Winter is coming, and you need to know the temperature/humidity in your home for heating purposes. You could buy a cheap gadget that tells you both values (boring). Or you could buy a Raspberry Pi and an external sensor, program it to continually upload its measurements into a smart home service and integrate that into a self-designed web app that plots current and past values and finally have a good overview of how your home is heated. Which is what I did, and what led to this small dashboard:

See it in action at here