Sonar — an app that uses Foursquare, Twitter, LinkedIn and Facebook data to tell you who is nearby and how you're connected — is launching the beta version of its long-awaited Android app on Tuesday.

Whereas previous versions of the app have focused on making connections within specific Foursquare venues, the new Android app uses "nearby" in a more relative sense. Instead of relying solely on Foursquare for location data, it brings Facebook and Twitter into the mix in order to cast a wider net. Through a combination of distance, time and social relevance, it determines the 15 to 25 most relevant people in the general vicinity rather than showing only who is in a specific room. It then plots them on a map.

Sonar has similar changes in mind for its iOS app that will roll out within the next week.

When you scroll through your list of relevant people, the app shows how you're connected. It notes when you have a LinkedIn, Facebook or Foursquare connection in common, both follow the same person on Twitter or follow each other on any network. The idea is to show you a starting point for conversation, and you can tweet at anyone who you'd like to connect with directly from the app.

Other startups such as Highlight and magnetU have also latched on to the idea of showing who's in the vicinity and what they have in common with you.

The major difference between Sonar and these other apps is that, by relying on social network location data rather than directly on GPS, the app can include people on your "relevant" list that aren't also Sonar users.

"It doesn't tell you just the people on Sonar," CEO Brett Martin says, "it’s a measurement of all the social media activity round you."

On the other hand, Sonar won't notice somebody who doesn't check in. Other apps that share location between users automatically don't have this problem.

Martin says a similar feature for Sonar is "a possibility."

The Android beta is invite-only, but you're invited. Use the code "Mashable" to get access.







Image courtesy of iStockphoto, gehringj