The company is holding an invite-only event in New York on September 28 but they are not saying what the event is about.

We have also written before on whether Amazon could scale this effort.

We will let you know more when we dig up some info from our sources.

The app allows participants to post status updates, and it displays their locations on a map, though they can tap 'leave' at any time and stop sharing their location. When the event expires, everything gets automatically cleaned up, and location sharing stops. It's kind of like Glympse but with group messaging features. We're In is currently only available for Windows Phone users in the U.S., but the post says the team is "working on bringing this app to more devices."

Google could integrate its calendars, maps and Huddle group messaging into a service like this. Facebook could combine events, Facebook Places, and its new Messenger app, which already has the location-sharing features. But neither of those Web giants could close the loop before Microsoft stepped in today.

As far as the platform, while Windows Phone 7 does not currently have much market share, an upcoming new OS version and new hardware from Nokia has the potential to stand out starkly from Android and iOS.

What do you think? Does We're In sound useful?

The most interesting part of the announcement is the inclusion of additional information by venue or event hosts. ESPN is partnering with Foursquare, for example, and is including both timeless Tips about sporting locations and after-action game summaries in the Foursquare news feed. If this points towards a larger trend of more, richer and more timely information becoming a big part of Foursquare, then that's a very good sign.

Indeed, the feature looks and feels big and new because it's introducing another dimension of engagement. In another way, though, this looks a lot like Foursquare brand pages - where organizations have had the option to publish sets of tips that would be pushed to their fans when they checked in at places. That hasn't caught on nearly as much as it ought to. This week's introduction of Tips Lists is another great feature that may or may not strike the fancy of users.

Will Foursquare's implementation of support for Events catch on with a significant number of publishers and will it work for users? If the future of location based services is changed dramatically by the expected rise of persistent location tracking, will Foursquare Events be able to meaningfully support new, real time use cases? Time will tell.

I really like this idea, but it's not clear that Foursquare itself is going to grow into a major social network. Whether publishers and users engage meaningfully with this new feature remains to be seen.