just curious... resting heart rate is a good indication of fitness level, no?

Pretty much. It can also tell whether U need to rest more to recover. Normally mine's below 50 bpm. Most health websites will tell U that 72 is the normal resting heart rate for human. The lowest resting heart rate I know of is former 5-time Tour de France champion, Miguel Indurain. He had a resting heart rate of 28, with lung capacity in excess of 80 litres (VO2 max).

if you workout regular then is ok to be low, if you do not work out then will have problem.This is call the diastolic blood pressure. The return blood flow.Correct me if i wrong....

Heart rate = heart beat per minute.
Diastolic blood pressure = the pressure in your blood vessels between heartbeats when your heart is resting (which is what you explained).