When Apple released iOS4, I wrote that the most overlooked functionality was the automatic calendar / event creator. Despite some flaws, it is a feature I use daily and it's a natural tie between multiple applications: email, contacts and calendars. These functions have also existed for phone numbers, addresses, URLs, etc.
And, as I just found out, they also exist for UPS and FedEx tracking numbers. It's terrific because it is simple, efficient and coordinated. I'd love to see more in iOS5 - almost as if they are plugins that can be switched on/off. For key brands, applications, actions, etc - it makes sense. For instance, Facebook hot-links, photo sharing / previewing, contact creation / sharing, etc.