I take my BP once a month. I have printed a grid of squares on which I write my readings. Ahead of my annual medication review I email my chart to the surgery. I also have a small pocket diary in which I record any health-related details and appointments to take along to any hospital or GP visits.
A lot of apps are far more complicated than I can be bothered with. For my daily steps I still use an old fashioned 3D pocket pedometer - so much easier to see at a glance.