buzzers

I would like to install some very, very loud sirens or alarm sounders which I can control from a relay or which plug in to main power socket, ideally one inside and one outside. I’d also like to install some moderately loud “beep” sounders or buzzers in much the same way. Any suggestions...

Does anybody know if its possible to retrofit the rear view mirror with the three buzzer buttons to open gates etc, in a w209 Any help would be great Cheers Kevin