Smartphone app startup Ripple Mobile today debuted its PhoneTag application, which uses GPS-based technology to help mobile device users share a user’s real-time location and coordinate connections privately with their friends and contacts.

PhoneTag lets a user select as many people as they want to be in a session — whether those people are contacts from their address book, someone they just met, business associates or anybody else with a smartphone. Users can set the duration of the session, or meeting, from one minute to “never ending.”

The system then sends a text message with a unique URL to the people the user has invited.

When those people accept and download the app, everyone in that session can see each other on a map, set a destination, text and call, get directions to each other, or simply chat.

Only the people who are invited to a session are able to see the location of others in the session.

If someone doesn’t have the app, they can still see the session and everyone who is actively in it through the website URL texted to them.

PhoneTag is available on iPhone, Android and BlackBerry.

The Dublin, Ohio-based company said its new app is designed to help users connect and even send step-by-step directions to each user’s location without broadcasting that news across all their social media networks.

This is a departure from similar apps, such as Foursquare, which automatically and publicly displays where a user has recently “checked-in,” or MeMap because of its privacy options.

Me Map puts data shared on Facebook and Facebook Connect by third-party location-based social networks like FoursquareGoWalla,Buzzd and others on one centralized map.

Ripple Mobile said its core technology platform was specifically designed to keep that information private, so that users looking for a spontaneous meeting can now share and receive location-based information for events and people along secure and confidential channels.

The company made news earlier this year when it debuted its OnTime mobile app, which syncs all of a user’s calendars and keeps track of meetings, tasks, to-do lists and local traffic patterns.

Co-founder Kevin Miller, who helped create the company in late 2010, told VentureBeat that it is currently aiming at a community of “smart device” owners that number around 200 million people.

Thus far, it has done well with PhoneTag, seeing a 40 percent growth during its public beta over the last few months despite the fact that it hasn’t advertised the app until today.

Ripple Mobile is currently self-funded and said it has no immediate plans to look for outside money.