Looking for a wireless doorbell type device, to be used as a remote security
call button. Ringer powered by batteries or plugs into mains socket, no
wires. Wireless between transmitter/receiver for ease of installation, able
to work through one wall at a distance of approximately 15-20 feet. Must
have a ringing or buzzing sound that cuts out when the button is released,
no annoying chimes that go on for ages. Loud enough so it can be heard over
disco music by someone standing 2-3 feet away from the bell/buzzer.

Can anyone recommend a specific product that can be purchased in shops, not
off the Internet. Cost is not really an issue, as I'm not paying for it out
of my own pocket, so not looking for cheap and nasty, but obviously the
person paying for it isn't going to pay silly prices.

Marcus