We bought one at the very beginning of lock down as I have chest problems.
Since then, our GP has asked all patients to buy their own BP monitor, thermometer and BP machine.
These all came in useful when I had Covid and again two days ago when I was able to give my GP all my readings: she immediately wanted to send me off to hospital by ambulance! I said we could manage and are not that decrepit.
The hospital diagnosed Pleurisy (possibly post-Covid, although I had that relatively mildly) and as we are now in a telephone-only consultation period, the GP was able to obtain data to help her make a diagnosis.
Yes, I think everyone should have all three pieces of kit. They are not too expensive. As long as one doesn't obsess over the readings, comes to understand over time what they mean and know how to interpret them, they are a great help all round.