Taking Notes With Your Finger

I use Google Keep on my Android phone to takes notes while I'm out on hikes, which is prime thinking time. Using the on-screen keyboard usually means I have to stop walking first, but I just noticed the little pen (circled in red below) which allows me to scribble with my finger, which even I can do while walking.

https://play.google.com/store/apps/details?id=com.google.android.keep