"I'm glad he doesn't respect me."

The words bothered Spock. They were illogical. Dr. McCoy knew that he respected him. He had informed the doctor of that fact only hours before when they were being surrounded by Krall's forces. McCoy was illogical, but his lack of logic followed a pattern as it was based on his emotional understanding of the situation. As the doctor had no reason to be emotionally distressed by the statement, Spock had to conclude that he was joking, the way he did when he pretended not to understand Vulcan biology. And, as he was aware of the great respect Spock had for him, Dr. McCoy should not be surprised by his decision to give both him and Captain Kirk tracking devices.

It was only logical. Though it had not been his intention with Nyota, it had proved most beneficial. Given Kirk's impressive ability to land in trouble having a secondary means of locating the man was wisest course of action. Similarly Dr. McCoy had a propensity for remaining with the injured, even in dangerous situations.

Spock was well aware that McCoy and Kirk were unlikely to be amenable to this logical measure to ensure their safety. Which meant that Spock would have to place the tracker on them without their knowledge. He was forced to dismiss the possibility of any subcutaneous device. Dr. McCoy would notice such a thing immediately. Instead, he embedded a trace amount of the same Vulcan mineral as Nyota's necklace in each of their StarFleet badge.

And if Spock meditated somewhat better after he had a secondary means of keeping the doctor and the captain safe, he kept it to himself.

Additionally he provided Nyota with the formula and infused his own badge with the mineral, just to make things equal, though he did neglect to mention that the necklace was made of the same material.

Also, as to why the same Vulcan mineral (I can't find the right spelling), he'd determined that any other device that could be used for a transporter lock would run out of power too quickly. Farther by embedding the tracker in the badges he could at least pretend he was respecting their privacy because they didn't wear the badges off duty... And this is where the comm badges in Next Gen came from. ^_^

And really I don't take this too seriously, it was just an idea that occurred to me when McCoy said that line (because it directly contradicted Spock earlier) and the idea wouldn't shut up until I wrote it. Which is why it is so short. Though I was thinking of writing a longer Trek fic and I might use this in that one.