The nice part of my circuit is that you don't need to continuously "pat" the dog. whenever you want to restart the circuit, you just drive the specified arduino output pin high or low depending on how it is initialized in the setup code. basically, the trigger pin of the 555 is held low and happy, then whenever it is triggered by arduino, the 555 sends a low to the arduino reset to restart the arduino. the 555 then keeps it low until its satisfied (determined by threshold resistor and cap values) then sends another happy high signal to the arduino reset to keep the arduino from restarting again.
FYI, the highs and lows in the above may be flipped and reversed, its been a good long while since i built and tinkered with the circuit. just remember, no patting of the dog in this