An app for Google Latitude briefly appeared on the Japanese iOS App Store yesterday, only to disappear a few hours later. Latitude is, of course, Google's persistent location-based service, allowing you to see where your friends are at on a map and share your own location in real time. There are already a few persistent location-based apps on the store, and there are even a few Google Latitude clients that access the service through the API -- not to mention that you can get to Latitude via Mobile Safari. But this was an official app, and it brought the service, which is already officially available on Android, over to the iOS platform.
It seems the listing was actually a mistake -- it quickly disappeared from the Japanese App Store, and it hasn't shown back up since. But it wouldn't be a surprise to see an official Google Latitude app on the App Store sooner or later, so this was likely a switch that was accidentally flipped a little early. We'll probably see the app live everywhere before long.