It's not the "few seconds" that's the problem, the problem is that it breaks the "flow" that you were in, such as switching tasks when concentrating hard or enjoying a jog or getting to sleep. The act of recording the data is quick but the mental jolt takes time to get over.

This is why passively recording the data is the way forward. I myself ordered one of these:

http://wakemate.com/

They're also a YC startup.