Apple released another new app today, Find My Friends (also requires iOS5), that allows you to selectively turn on the location/GPS and allow people to see where you are - or you to see where they are.
It's the perfect app for those concerned about sharing their every move on other sites like Gowalla, Facebook and Foursquare where everything is wide open unless you turn on the security settings.
You can do things such as set a temporary time that your location is available to certain people, as seen in the screenshot below:
So if you're at a conference or a family vacation at Disneyland, you could allow everyone you know to see where you are so you can more easily meet up and find each other.
As I said on a recent episode of Too Lazy to Blog, it's one of those features that sounds really good when talked up - but most people probably won't use it that often.