Decreased fetal movement is a valid and important indicator of fetal distress. I know it is sort of the culture around here to question most medical advice and to assume that all is well... but a decrease in fetal movement should never be ignored. As far as fetal monitoring goes, it is completely natural - requires nothing other than a little quiet time. Lots of mamas enjoy doing kick counts because it's a chance to focus on their baby, and they feel it is a bonding time. Kick counts are a way to quantify fetal movement. It gives you specific data to look at rather than just a general "maybe he's moving less" feeling. It's especially useful in high risk pregnancies.
If you are feeling your baby moving throughout the day, don't sweat it. But if you notice there *may* be a decrease in movement, then a kick count is a good idea. Some mamas do them regularly because they have a high risk pregnancy or because they find it reassuring.
Decreased fetal movement is often the first, and only, sign the baby is in trouble. If you are in tune with your baby and you can catch this early, you may be able to save your baby's life.
I'm not saying this is something to obsess about or fret over. But being aware of fetal movement is important. Kick counts, for many women, is the best way to monitor fetal movement.
http://www.countthekicks.me/