Hey there Tchen811.
BMW offers an extended "maintenance" package, but not an extended warranty. I bought the maintenance package. It normally costs $1600, but I got my dealer to pick up half the cost at the time I bought my car. It extends the standard "maintenance" coverage from 4 years / 50,000 miles to 6 years / 100,000 miles. It covers oil changes, major inspection services ( like inspection 1, inspection 2), brakes, etc. However, it does not extend the factory "warranty" on parts, etc., doesn't cover my convertible top (or associated mechanisms), doesn't cover lighting, powertrain, etc.
Hope this helps.