Imagine you and a friend are on a phone call, and both of you own iPhones. You're trying to meet up somewhere downtown in a city neither of you know very well, so the best answer you can give your friend when he asks, "Where are you now?" is "Uhhh..." followed by several seconds of silence. It's already possible to share your location using the Maps app on the iPhone -- find your current location, tap on the blue marker on the map, tap "Share Location," and then send it to your friend either as an e-mail or MMS. Then your friend receives the e-mail or MMS with your location, opens it in Maps, and has the option of finding directions to your location from his current location.
If that sounds like a lot of unnecessarily complex steps to answer the simple question of "Where are you," you're in luck, because according to a new patent application, Apple agrees with you. By putting "Request location info" and "Release location info" buttons on the call screen in the Phone app, it would be possible to share your location or request someone else's with a single button press. The same process applies -- the iPhone polls its GPS to find out where you are, then transmits that info to your friend's iPhone -- but instead of having to jump through all the hoops yourself, the OS handles it for you in the background. Once your phone receives a request for location info it comes up in a notification, probably very similar to the notifications location-based apps already use when they request permission to use location data. If you agree to release your location data to the caller, it's transmitted in a fully encrypted signal to the caller's iPhone. Your location data would then show up on your friend's iPhone, complete with the option to find directions.