Bounty Hunter 17 (Source)

The only real tracking help you would want at master is the tracking droids. At master the speed updates once about every 10 or 15 seconds, and you update 12 times. So if you add more speed, your updates come to your faster, however, your 12 updates expire faster which isn't good at all....

They're a measure of the effectiveness of your use of Arakyd Probe Droids and Seeker Probe Droids. For the Arakyds, a higher rating results in a reduced likelihood that your Arakyd will malfunction in space -- things like, "Your droid has been eaten by a space slug" or "Your droid has been destroyed by a comet." For Seekers, once you gain the ability to "Find and track target," improved numbers result in longer and longer stretches where your droid updates your target's location.