Depending on what your trade is, you often need prototypes of things that do stuff. Before Arduino is usually cost thousands of dollars to make these (only coun

Depending on what your trade is, you often need prototypes of things that do stuff. Before Arduino is usually cost thousands of dollars to make these (only counting the hardware cost). Arduino drove that price down to a fraction. It's easy to develop pretty much everything in very little time. Here are couple rather uncommon examples: - a greeting card with an integrated mobile baseband that calls a certain number once opened ("hey grandma!") - a tea-timer that automatically pulls out the teabag after a set amount of time - a UV-dosimeter that measures the actual amount of UV exposure and connects to your smartphone to track the data and warn of potential damage (with respect to your skin-type). - the DIY-cellphone by David Mellis modified to display reading from arbitrary sensors Your imagination is the limit. ;)