The Yellowbrick essentially does two things, GPS tracking and two-way messaging.
While there is no mapping functionality on the device itself, the GPS reports your location automatically at set intervals. This can be sent to an online map (each device purchased is provided with a live online map and blog page to use if you wish), or as e-mails or text messages to previously defined e-mail addresses or phone numbers (or any combination of these).
http://www.bushwalkingblog.com.au/revie ... messenger/