the watch you plan on using, is it metal or something nonconductive?
if it is metal, you might want to put a resistor into the circuit (yes, i know it was mentioned earlier). perhaps a pot for...adjusting between those who are more difficult or easy to awaken.
if i were to do this, i would use a transformer to convert 120v or 220 volts to about 24v, use a nonconductive watch and incorporate 2 electrodes on opposite sides of the watch.
you could use a basic mechanical timer with buttons to start and stop the timer.