I actually had my BMR measured at a gym I was using a few years ago. They use a device called an indirect calorimeter that you breathe into. The company that makes it is
If this measurement is accurate, you can calculate your daily caloric requirements using their software. When I did the test, it correlated very well with the Katch-McArdle formula formula based on lean body mass. Of course, the LBM measurement has to be accurate too.
As for recording what you eat, I am right with you there. It is very easy in the beginning to miss a lot unless you write it down. I have been at this for a long time and I don't record what I eat any more. Perhaps I should get back to it. I still weigh almost everything though and am pretty confident about my intake. I will try tinkering with the number of zone blocks I eat and see where it gets me.