A month ago, Lyft announced, almost simultaneously with Uber, its Line ride-sharing service. At the time, Line was only available in San Francisco and accessible from the service's iOS app. The location limitation is still there, but Line has just made its way to the Android side through an update to the Lyft app.
To share a cab, you must go to the Line tab and request a ride. After you set your destination, Lyft will find cabs heading in the same direction and that would only require a small detour to accommodate both your and the existing passenger's routes.
The first Line ride should be free if it costs less than $25, after which you should expect to make savings up to 60% on your ride fares when you use Line. If you live in San Francisco and want to use the feature, it's only a download—or an update—away.