What is the interval should be between a coitus and blood pressure measurement or other physical activities ?

15 minutes: Rest for 15 minute before checking bp.

15-30 minutes: If you are involved in low intensity activities (walking, light housework), i suggest no less than 10-15 minutes before you take your blood pressure. Any intense physical activities - coitus, sports, smoking, caffeinated beverages - ideally no less than 30.

Minimal : BP should generally taken as a resting measurement, so a few minutes of rest and relaxation should be sufficient to give a resting measurement. If your heart rate is back to normal, and you're breathing comfortably, that should be fine. In general, there's no need to delay exercise or other physical activity unless you have significant medical problems that might affect physical activity.