With SXSW starting Friday in Austin, Texas, every location-based service out there is right now finalizing updates that they hope will be the one that gets them used more than all the others. Loopt, is betting on events integration.

The latest version of the app, due to hit the App Store tomorrow will feature a new Pulse tab. Here you’ll find events populated from a ton of sources including the live music tracker SonicLiving (SXSW is first and foremost a music event, after all) and most notably, Facebook. This pre-population is important, because it means the events will already be in the system so users won’t have to do anything other than share it with friends, or check-in if they’re going. The feature also uses you current location to show which events are happening around you at any given moment that a lot of people are at.

As you might expect, you also also tell who is already at the event, and which of your friend is supposed to be going. The later feature works with Facebook Connect. You can RSVP to an event right from within Loopt and see who else is scheduled to go.

Calling it the “best event ever from an app,” Loopt founder Sam Altman believes they’ll have every single event taking place at SXSW in their system. A newer startup, the recently funded Plancast (started by TechCrunch alum Mark Hendrickson), may have something to say about that statement as they’ll be debuting their own events-based iPhone app at the festival as well. And like this new Loopt feature, a key Plancast component is Facebook event integration.

Loopt was one of the original hot players in the location space, launching an iPhone app alongside the App Store launch in 2008. However, their initial bet was on always-on location updates, which the iPhone cannot do because it will not allow third-party apps to run in the background. Loopt found a loophole (see what I did there?) to that through AT&T, but by then the momentum has already swung to the check-in based location services like Foursquare and Gowalla. Last year, Loopt pivoted its app to be more predicated around check-ins.

Look for the latest Loopt app tomorrow in the App Store.

Disclosure: Loopt offers a TechCrunch branded version of the service here.