I have found this a very interesting topic. From my perspective and 33 years in the industry you have all very valid points to consider.
One of the posts said that they have never heard of a GM coming from a service background.
Here is a little of my history.
13 years as a road mechanic. I started in a grease truck and eventually was one of those premadona road toads who wanted to work 4 hours, billed 8 to 10 for the company and thought I should be allowed to go home at noon. My customers loved me right. Never a complaint about a bill! What's the problem.
Spent one year as an aftermarket salesman, during that year I realized what it was like to have to be the one to go and see the customer when he didn't need anything; suddenly I was no longer the hero. During this year I gained new respect for what sales people go through.
After complaining enough about a bad service manager at the company I was asked if I could do it better. Not thinking before I spoke the next thing I knew that was my new title. Service Manager. I did that job for 8 years at two different companies.
One day I got a call from the factory and next thing I knew I was the regional manager for 26 states.
Next a Branch Manager for 10 years and very recently I accepted the title of GM
240 employee's and over 100 road mechanics in vans.
I have seen many things come and go in the service side of our business over the years but the topic of abusing time is still an issue that drives management crazy.
Here are a few thoughts I have.
Do I have GPS- Yes on every van, transport truck and parts trucks. For over three years now
Do I save on fuel- Yes over 18% reduction since implementation.
Do I save on insurance- Yes 10% annually.
Is it a tool- yes
Is it used to provide customer service- yes
Does it control speeding- yes
Has it improved our response time- Yes
Is it used for anything else- Yes, We use it to receive time cards, parts tickets and bill directly from the information.
Did we have push back - Yes
Did we lose mechanics because of it - Yes
Was it bypassed- Yes
Have I ever terminated or disciplined from its information - yes
Have we improved on productivity - Yes
Have we used it to defend a mechanic who had it reported that he was not at the customers for as long as he said - Yes
Have we used it to credit a customer when it was reported that a mechanic was not there as long as he was billed - Yes
Have we been able to keep rates down because of its use -Yes
Do we use it daily to check up on mechanics - No
Do we use it as a primary tool to discipline - No
The main point I wanted to make is that GPS can be used for good things. The customer is the real beneficiary when it is used correctly.
I understand how it can be seen as a BIG BROTHER and used to make up for management deficiancies.
I look at it this way
If I have to take off a 3/8 nut and have two wrenches in my hand, One a 9/16 boxed end and the other a crescent wrench. Both will do the job but one has higher risk than the other of causing damage to the nut.
What one would you chose.

Don't ever forget your roots if you do move up, and don't ever try to understand the problems of a job you have no experience at. Communication is the key to the best customer service. Keep that open and you will always sleep good at night.

I respect everyone in our industry and have never forgot that the mechanics our our front line.