I opened my email today on my iPhone 4 and discovered that iOS 4 now detects various tracking numbers and links them to the appropriate tracking website. Not a huge find, but defiantly useful hidden feature of iOS 4. Click on a tracking number in your email, and Apple will present you with the following screen. When you click “Track Shipment” iOS 4 will figure out which shipping provider the number applies to and will link you to the appropriate tracking website.

Have you found any not so well known features in iOS 4?