A stress-free and relaxing tea time (or coffee time or [insert hot beverage of your choice here] time) in a cozy corner can take an abrupt halt when your tea is scalding hot. All of a sudden your cozy corner is a death lair that leaves you with a burning tongue. Leave it to a creative and constructive techie to solve the problem of sipping on too-hot drinks with a little LED...
If you're a crafty "nekojita" (the Japanese term for a person who can't handle hot food. It means "cat-tongue" and was coined after like-minded felines) like the person behind this DIY project we spotted on Instructables, then you better find yourself some colored LEDs and a temperature sensor and get to crafting your very own temperature-sensitive coaster.
This particular one lights up red if the drink is too hot, white of the drink is too cold and green if the drink is just right.
If you also trick out your coaster with a tilt switch, you can re-calibrate the "just right" setting each time you make a drink, just by tilting the thing to one side. A bonus for those who need their coffee hot but their milk cold.
Check out the whole Instructable article here.