In at least 90% of the crashes I have witnessed (at least twenty) the battery has always been disconnected from the reciever. You are far better off to have the alarm or beacon be a self contained power supply and audio alarm that is constructed to alarm only when the self contained switch is on and the signal from the reciever is missing. You can build one up fairly simply by using an LM555, a 9 volt battery and a Radio Shack buzzer. Just hook up the LM555 as a Pulse Emission Detector that is continously reset by a valid signal from the reciever (it plugs in like a servo would in a spare channel or on a Y to any other channel). Now, when you switch it on and are getting good signals, the audio stays off, but if you loose the radio signal for a second or two, the alarm starts going until you get another good radio signal.