What's The Most Under Appreciated Piece Of Car Technology?

Cars are full of tech. Some of it is intrusive and annoying. But a lot of it is in the background and we never even think about it. What piece of tech do we need to appreciate more?

There is an obvious answer that has been saving lives for ages, yet we take it for granted on almost every single new car. That feature is ABS.

Anti-lock brakes are a huge advance that have assisted control and safety for ages, but have now become so ubiquitous that we don't even have to tick it off on the option box anymore.

But what say you? What piece of car tech do we take for granted?