Entirely your decision.
Regarding what use they are - similarly to blood glucose testing, it gives a fuller picture of how the individual reacts from taking different readings in various typical circumstances. For instance, for me - which doesn't mean it will be for everybody - there are specific situations where my BP rises to "help" me through whatever is happening at the time. Therefore I get a picture of what my BP is doing in various circumstances and so don't judge my overall health on a single reading at a random time. BP like BG is a reactive system designed to help us survive.