Workshop. A problem to solve.

A painter (while he are painting) has two hands busy. Left hand he has a palette and another hand he has a paint-brush. He needs do notes and check marks on app. He can't use his hands.

What I have: android, arduino, raspberry pi, electronics and B4X of course.
How create a solution? Simple. Elegant... Cheap...

For now I thought about two possibilities.

voice.
openCV (the paint-brush would be a virtual pen)

Do you have another suggestions?

The possibilities are different:

1. Reading thought with Google Telepatia Library
2. A micro USB connector in the nape directly connected to Raspberry
3. A digital pen that land in the mouth that transmits the movements in an Android device
4. Morse code transmitted by blinking eyelids

A fairly simple problem to solve as there already are established solutions out there.

To help painting: traditional overhead projector (very cheap to get a used one)
(could be swapped with a projector that you hook up to the mobile if you want/need a more modern solution - probably more expensive)

To help note-taking: voice-activated audio recorder (probably exist lots and lots of these in the app store already)

1) You can use a Touch screen pencil tip in the back side of the brush
2) Use USB Pedals.

https://www.amazon.com/iKKEGOL-Control-Customized-keyboard-Multimedia/dp/B07553KW32/ref=sr_1_6?crid=1RG348DTILDK8&keywords=pedals+pc&qid=1556379364&s=electronics&sprefix=pedals,electronics,284&sr=1-6