I made a little device that helps to tell you what temperature your cup of cuppa is from the colour of the led light strip. Basically, warmer -> reddish undertone, colder (and nearer to room temperature) -> blueish undertone.
However, the temperature sensor took quite some time to sense the change in temperature, hence it might be better to use it to test when your hot water has sufficiently cooled, rather than how hot it is. As waiting for the hot water to cool down has a somewhat similar (ie. longer) timeframe available for the temperature sensor to sense the actual temperature.
Up: Final Prototype
How it was made:
The temperature sensor poked through a tiny hole in the cardboard. Place the cup above this hole.
An example of different colours the LEDs were capable of. Blue (cold), Red (warm)
An Arduino Uno, and Adafruit library was used to make the code.