This simple circuit is designed to report the temperature via any standard FM broadcast band radio at regular intervals. It uses a simple low bit rate tone signalling scheme which can be interpreted easily by both humans and machines. Such a device can be used stand-alone or as part of a PC-based weather station or HVAC system.
There are endless practical applications for such a device, just think about how many time you wanted to measure a temperature and for that you needed to run wires to the sensor. Now with this circuit you can place the device where you need the temperature reading and no more wires need to be connected.
Wireless Digital Thermometer: [Link]