human sensitivity to shock loads
There is an idea from italian b-ticino.
When the socket is empty the voltage between tghe poles is 12 V or similar.
When you insert the plug, the circuit test for lekage and if everithing is OK it delivers the mains voltage ( here 230 V ).
The circuiti is quite small, say 2 * 4 * 2 cm, it works up to 16 A current and is working well.
Actually it is embedded insude the socket.
I have no idea about the schematic diagram, but is solt at about 15 Dollars ( 12 Euro ) each.
Mandi