I am not convinced the electronic gadgets like that are of much use to us without a dyno. I also have many reservations about the use of them but that's a discussion for another thread. Det cans on the other hand ,IMO,will tell even a novice if there is any detonation occurring instantly and without a doubt. Are they sophisticated real time EC tuning aids? Nope. Are they cheap? Maybe,depends if old school stethoscope type or more modern microphone types but either are pretty inexpensive. From what I've read ,the old school ,non electronic type ,are preferred by many tuners and they are dirt cheap to fab. I got interested in this a few weeks ago. I have never used det cans of any type ever. I am only passing on my thoughts. I have though used a mechanics stethoscope many times trying to isolate an engine noise that just was impossible to isolate. I recently again used it to find a tick in an engine. It got me to thinking again about det cans.Honestly,a person can plainly hear every noise in an engine with the stethoscope.Every rocker,every piston slap,etc.. You know what I mean if you've used one. This got me thinking .......................... More to come.