Design a simple transmitter and receiver

Hi,
i am currently working on a car project. I am trying to design a
transmitter which can send a predetermined message to a particular
receiver. the transmitter will be placed in a car and will send a
signal to a pager/ receiver if the car gets too hot standing in the
sun. average range of the signal should be aroung 100m. does anyone
have any material as to how to design such a transmitter and receiver?
thankyou.

 

Microchip have some sinlge-chip solutions for this kind of thing.

www.microchip.com