RF communication using MCU

I need to design a RF transmitter circuit and a receiver circuit.
the transmitter should be transmitting signal(can be data or digits also) at all time. If the receiver cannot detect the signal or out of range, the receiver will sound a Buzzer and light a LED. the buzzer and LED is done... so i need the transmitter and receiver circuit...btw my circuits are pic16F628 or 8051(which 1 suitable?), RF Transmitter 315MHz, RF Receiver 315MHz,
Buzzer-PCB Mount. Thanks.