"fastidious characters whose cars approach perfection. (And Bill-qaz checks everything “before every outing”. I bet he includes the hydraulic oil too.)"
My car is far from perfection or standard, it doesn't use enough oil to require mid journey top ups. I have oil pressure and temperature gauges I keep an eye on during driving.The things I mentioned are just routine daily checks that were normal when the car was made. I check other service items regularly as well. But that is also because I enjoy doing these things as part of the classic car ownership. Its the same routine on the other 4 classic vehicles I maintain and drive on behalf of the owner.
If the op wants to fit the device, then great its his choice, his car.
As I said to each their own
PS still looking for where the hydraulic oil is
