Are you looking to see where the other person is at? If so, you have a couple options. You can use your blackberry maps with the gps turned on and send the other person your location through BBM. Also, there is a new feature from Google through their apps called latitude that you could sign up and install google maps on your BB and you can share location their. As a warning, Google maps uses cell tower triangulation by default instead of GPS and is sometimes off on location.
I just read about Loopt and have heard good things about it. I have not tried it yet however.