Although there's many temperature-reporting projects out there based on various sensors, this project by Instructables user Blockman301 is an interesting alternative. Instead of just reporting whether the temperature has risen or fallen from a set level - it instead takes the average temperature over time to determine what is "normal", and then detects if the temperature has suddenly dropped.
This can be useful when searching for drafts though windows, doors or areas where HVAC isn't effective. The system uses inexpensive thermistors which are measured with an Arduino-compaible circuit to determine temperatures, and the sketch can take care of the rest. The interface is quite simple, and switches between a green and red LED when the temperature has altered.
If you're wanting to make your own Arduino-compatible project such as the monitor above, you'll need an ATmega328P MCU with Arduino Uno bootloader:
This is the same Atmel AVR ATmega328P microcontroller used in the official Arduino Uno, as well as our Eleven, EtherTen, USBDroid, and other boards. Perfect for building your own Arduino-compatible project directly on a breadboard or on a custom PCB, or for replacing the MCU in an existing board. Comes with the Arduino Uno bootloader pre-installed. Better still, it even has a special label stuck on top with details of the pinout, so you don't even need to look up the datasheet when connecting it up in your project! For more information and to order, click here!