Pretty design, eh?

Apart from the highly overpriced RS-80N3 remote switch, the components above were bought at the local DIY shop for less than SEK 100 (< US$ 12)

The pushbutton is your portable trigger and although the stated range was 30m (100ft), the practical free-sight range is about 10-15m. I have recently bought a more sophisticated (SEK 150) door chime which works in the 433MHz ISM band (as opposed to the one above, which is a 868MHz one) and its stated 100m (300ft) range seems to be at least 50m.