I have two of these from several years ago and they still work perfectly. http://www.nelsonhobby.com/advanced_glow_switch.php They work independently of the throttle setting and sense when the plug is cooling and turn on. With the other ones operation is dependent on throttle setting even if you adjust it for your particular model. That means at some point in time the glo plug will not re-light and the engine could quit. The Nelson one senses the plug loading up and turns on. Expensive but works better than any of the others I have tried. Heck you can buy a 2000 ma or better nicad and a roller switch and make your own if all you want to do is turn it on at a low throttle setting by having the servo arm depress the roller arm. An on/off switch for power and some sort of charge jack and there you have it a simple on board glo set up.

Dennis