I never bought extended warranties until I bought a big screen DLP tv a few years ago. Over my short 4 years of ownership, the repair man and I became good friends. He was over so much that I almost got him a Christmas present.
The replacement parts for that set far exceeded the cost of the tv, due to the manufacturer streamlining their production process by putting virtually everything on one board - which was expensive.
Needless to say, on the expiration of the warranty, the tv left the house via the same door it cam in through.
I just had a navigation head unit replaced on another of my vehicles - under warranty. To stay OEM the new unit was over $2000 from the dealer. The unit itself worked fine except for the bluetooth mic. Due to the way the unit was built, fixing anything means replacing the whole thing.
If this happened after warranty, I'd probably go with an aftermarket unit for under $1000 installed, but the fact remains that the warranties on even Hyundai's have limitations on them for some very expensive components.
The warranties I have seen that are sold by dealers, do cover these components up to the time and mileage limit of the warranty. Most usual is extending coverage to 10 year/100,000 bumper to bumper.
It is important to verify this if you are considering purchasing an extended warranty and not just assume the things you are concerned about are covered. One thing to really look for is if the dealer sells things that they title "Gold" "Silver" or "Bronze" type plans. Unless you consider the top tier, your chances of getting what you really want protected are pretty slim.