help.. rf proximity alarm

[stevedavis]

hi there, i am trying to build a circuit that will eventualy become an rf proximity alarm of sorts. it must be small and low powered with a transmitter and reciever. if the reciever gets within aproximately 5 to 6 feet of the transmitter it will trigger the alarm. can anyone help please. i used to build a lot of electronic projects and am a mere amature and have been out of the loop for a lot of years. in other words simple circuits are my option. any help would be greatly appreciated.

 

[MikeMl]

What do you consider low power? You can buy turnkey transmitter and receiver modules. How much are you willing to spend?