Are there valid reasons for recording a salesperson’s travels by GPS? Short term I am sure a team's sales would increase due to the bottom performers running scared and working harder. But long term I believe a team will lose its top performers (or future top performers) due to their feelings of “Big Brother” and the direct message of "we don't trust you" that tracking would send.
Sometimes a looser rein gives you more speed out of your top performers, like a horse rider with "quiet hands" on the reins produces better performance from the horse. I believe by using GPS tracking a manager would ultimately see a loss in productivity due to the sales reps quickly learning you will question any variance in their records to your GPS data.
As soon as your sales reps learn of the potential of being challenged then they will start keeping additional more detailed logs of where they have been and when, a function that will do nothing to increase your sales. All airline mechanics keep their own detailed paper logs of every piece of equipment worked on and what they did, copious notes, preparing to defend themselves in case they were the last mechanics to have worked on a plane that had crashed. This takes hours away from their productivity each week. I have heard it is even written into their union contract to allow time for their own personal records.
I believe there are other ways to measure and track the performance of sales reps, and that is what they accomplish and how they talk about their accounts with their managers. If the manager is acting like a “Selling Process” sales manager, occasionally riding with each rep and conducting ongoing one-on-one coaching sessions, discussing specific accounts, the manager will quickly weed out your under-performers and laggards.