http://www.burneralert.com/simulator.html
This is the best solution I have seen for this problem. It sends a beeping noise every few minutes to remind you the burner is still on. My microwave has a similar reminder that I have left something in there after it finished cooking that I find very helpful. This would probably be just as effective. You put them on your burner knobs. If you leave a knob without one if you want to cook something for a long time you can choose to do that on a burner you find you don't use often like the one the tea kettle is on. I leave the kettle on that one most of the time in case I turn that burner on by accident which would make the kettle whistle after a time. If I'm going to keep something on the burner on very low like when cooking beans I set a timer. After I left eggs boiling on the stove and came back to eggs exploding all over the place when the water boiled out i don't trust myself. I mean, who wants to stand over the burner doing nothing for 15 minutes? Okay, blame the ADD but luckily there now is a solution for people like me. This is very late but I think the things only came out recently.