The latest version of Loopt’s location service app for iPhone and iPod Touch now lets users view and create Facebook Places check-ins through an integration with the Places API. The app’s users see both Loopt and Places check-ins on their map, and Loopt check-ins published to Facebook will appear on corresponding Places pages and the “Here Now” list. Users can also now be alerted when specific friends are within a certain proximity.

At one point, there were rumors that Facebook was interested in acquiring Loopt, but then the location service was not selected to join competitors Foursquare, Gowalla, Yelp and Booyah as a launch partner for Facebook Places.

When users of the new version of the Loopt app view their interactive map, they’ll see icons representing the locations of their Facebook friends who’ve checked in with Places in addition to Loopt check-ins by their Loopt friends. For many, this will populate their map with many more check-ins, making it easier to find someone to meet up with. Friends who check in through Places show a Facebook logo in the bottom right hand corner of their profile picture shown when their map icon is tapped.

Users will see a list of Places nearby when they go to check in through Loopt. Clicking a Place brings up a check-in composer where the user can add optional text, upload a photo, and select whether to share to Facebook or Twitter as well as Loopt. When shared to Facebook, the check-in is posted to a user’s wall, the feeds of friends, and the Places page for that location. The ability to include a photo is an improvement on the native Facebook Places interface for iPhone and iPod Touch, though the photo will only appear in the feed story, not on the Places page.

Other improvements to the app include the ability to be alerted when a selected friend comes within a chosen proximity of you. For instance, users could select to be notified when specific out-of-town friends come within 10 miles of them. Users can also now use their email address to register for a Loopt account, while previously users had to register with their phone number. Distribution of Loopt content is limited by both the app and Facebook’s privacy settings.

With Loopt taking advantage of the Facebook location platform, now all the major location services can syndicate check-ins to Facebook. While users of the different services gain from the ability to distribute to and view check-ins from a larger audience, Facebook is managing to make itself the back bone of location aggregation.