I beg to differ on the statement "Extremely unnecessary technology"

I beleive a knock sensor like this is very necessary. Wideband A/F for piece of mind (also good for tuner). Knock Sensor, most performance cars are tuned with 98oct (highest oct on pump) and pretty agressively (just before the point of premature ignition AKA - Knock/Ping)

Sometimes its hard to hear a ping with a loud exhaust, with this unit you can SEE it on the head up display and Head it through head phones (good for drag or circuit to alway have a set of headphones in to listen to engine knock). This is for worst case senario if you ever get a bad batch of fuel and you start pinging... then you simply know when to put in octane booster (which you should always keep in your car if you want to keep a performance engine healthy.