Having just called them, the decision to install a tracker is literally on a case by case basis, not specific to our distance from him, simply because of the distribution of our family unit. Additionally as he is full of anxiety they would be happy for the case chat to be with his wife and or myself to explain our plans. If a tracker were to be fitted, mileage is irrelevant (as long as under 60k over the 3 years) but the frequency of journeys that include my father in law that is important. Strangely my father in law would consider me running errands for his mother (our nan) to be a benefit to him as it would reduce his stress and anxiety as he is unable to do so himself, despite her being 87 and fiercely independent!
So we will apply and see how the eligibility interview goes, doubt my father in law would be keen on a tracker as he is ex forces!!