Add another carrier to the growing list connecting with Loopt’s friend-connection service. MetroPCS is the latest one to sign on.

Loopt’s goal is to be available on all carriers so users don’t have to worry about which phone or carrier they’re using. So far, it has deals to work with the networks of Boost, Sprint, Nextel, Verizon Wireless, T-Mobile USA (for BlackBerries) and AT&T with the iPhone.

With MetroPCS, Loopt is available on the Motorola RAZR and ROKR and the Samsung U520 and MyShot (R430). On its company blog earlier this week, Loopt said it soon will be supported on many more devices in MetroPCS stores.

Loopt will be free to all MetroPCS subscribers for the first month of use. It is included free of charge in the $50 calling plan and in the $40 and $45 calling plans at $4 per month.