It occurs to me that the voice recognition system seems a bit of overkill when you have to pick up the radio and talk to it. You could use VOX, (where the radio switches to transmit when it hears sound), but then it would transmit every sound in the house, not a good idea!
Why not create a keypad which sends tones via the radio to do the switching? Again, someone could record and playback the tones, but at least they would have no idea what it was for, and so would not bother.
JimB