What would be a complex switching scheme otherwise, becomes a piece-o-cake in a low voltage system. Switching any number of loads on and/or off becomes a simple matter of using a diode matrix. The only limiting factor would be the additive currents of relay coils, exceeding the ampacity of switches or the power supply.
I remember building a couple of PCBs for outdoor lighting control. A tap on the off button caused a several minute off-delay while holding the button for 3 seconds turned the lights off without further delay. I could have just as easily put in a control to turn the same lights on if the dog barked. On a more practical note, those relay boards they sell that connect to a parallel printer port, and a few more diodes, would have added computer control to the matrix. Once you have 3 wires into a 2 switch combo, control possibilities are limited by your imagination instead of the number of conductors.
Joe
