you know those lamps that you touch and they anything else like a book other metal etc. the only other thing I found they turn on with is if you touch them with certain fruit. How do they work?
how they work depends on it its a capacitance touch swtch or a resistance touch switch.
capacitance switches are the more common one and they use the body's natural capacitance, the switch has a small electrical charge which when touched the overall capacitance changes and triggers the switch
BTW the body's natural capacitance is why we can build up a static charge and get a shock sometimes when we touch things
capitence (sic) is basically stored electricity (or potential difference to be precise) your phone would have triggered a touch switch because the radio energy it uses is a small electrical charge.
Not sure about the melon, I can only assume that as it was being touched at the same time as it touched the switch it conducted the body's small charge to the switch.
Though I am also slightly worried about anyone that takes a melon to bed!!
Ouch my head is hurting, been too long since I done electronics at collage.
I have no idea about the book, sure sombody who,either, has studied this sort of stuff more recently, or paid more attention that I did will come along and answer :)