I can't answer for the OP but I have used them a long time ago in cowled planes just to make things easier for me. I started making up my own remote glow drivers and gave up on the on board systems for years until this month. I have one engine that is tight cowled, the remote glow driver works OK on it. The engine is inverted and runs great but with an on board the idle smooths out a lot better. I made up an on board a week ago for this plane but didn't like the set up so I pulled it. I may make up another one this winter?
The hobby is full of danger the moment the engine is started, having an extra switch right next to the RX switch isn't all that more dangerous unless your some sort of DA, in that case you may as well take up something like watching TV. Nothing wrong with thinking safety but what the heck, some people shouldn't be allowed anything with a sharp point.