Just install a 2-hour wall timer between the mains and the stove. Trigger the timer before cooking, it will cut the power to the stove after 2 hours (whether it is on or not). These timers are quite common in communal kitchens, e.g. in hostels. There are plug-in versions for devices like water boilers or clothes irons. No high-tech needed, always works. If you're broiling a mega-turkey you might want to restart the timer before it runs out, otherwise you won't notice it is there.