Well, going route #1, I'd like this to circuit to be pretty generic. In other words, be able to work with various radar detectors. Obviously, each will have it's own idle current (quite low) but when lights/alarm on the unit goes off, the draw will certainly change. Of course, the detectors work on roughly 10 to 15 volts DC. On the output side of the circuit, it really only needs to be a latching relay or something similar to drive an external 12v siren, light, or whatever.