Having a few Smart Coasters to jazz up your tabletop is sure to get the conversation going when you have folks over. That's because the coaster can sense whether the drink on top of it is hot or cold, and then it'll light up red or blue, respectively — and giving the drink above it a bit of color. All of its internals are safely tucked inside a shell of molded plastic, too, so that means they're good to wash.
Smart Coasters are a creation by Evil Mad Scientist, who you may remember for creating this little gem. The coasters are one of the DIY projects in The Hungry Scientist Handbook, a collection of several tech-minded projects that show you how to use some easy-to-find technology to geek out your dinner parties. Just be careful when you put the Smart Coasters together — they use a methyl ethyl ketone peroxide catalyst, which is explosive.