Google has finally released a native iPhone app for Google Latitude. The web app is nice, but you can't use it to update your location in the background. Google Latitude for iPhone uses one of the new features in iOS 4 that allows applications to track your location even if they aren't in the foreground. That's the main reason why it requires an iPhone 3GS, iPhone 4 or iPad 3G running iOS 4. (Update: According to Google, "the Google Latitude app will run on the iPhone 3GS, iPhone 4, iPad, and iPod touch (3rd/4th generation). However, background location updating is only supported on the iPhone 3GS, iPhone 4, and iPad 3G.")
The native app is better because it shows more information about the locations of your friends and it sends you to the map view when you click on a friend, but the web app is just a layer in Google Maps and this makes a lot of sense. Google Latitude should not be a standalone app, it should integrate with Google Maps and Google Contacts, so you can quickly find your friends.
Marissa Mayer, Google's VP of geographic and local services, has recently said that Google Latitude will add explicit check-ins, inspired by Foursquare. "Latitude is useful for a smaller group of people. Only a handful of people you'll want to know where you are at all times. There will be new layers coming on top of it. It's more useful when more people are on it. And implicit and explicit — yes, the check-in. Maybe that's in Latitude or maybe it's in Maps."