For just a couple of bucks and a few components you have laying around your work area you can build a min thermometer than fits in your pocket. The whole circuit sits nicely right on top of a 9v battery, and is connected to it with double sided tape. Changing batteries was never so easy!
I hope you enjoy the project and vote it for the contests!
In case you were wondering why the LEDs are flashing multiple times on each flash it's because I'm using PWM to power the pins.