como puedo hacer para convertir escritura a mano alzada en texto digital, ayuda por favor.
How convert handwriting to digital text.
Here an ocr extension by Mika (year 2017).
you might want to try the suggestion by @Juan_Antonio
Taifun
Trying to push the limits! Snippets, Tutorials and Extensions from Pura Vida Apps by 
Taifun.
You might be able to use an ActivityStarter to command a handwriting app . Google Handwriting Input is a stand-alone keyboard which allows you to handwrite text on your phone or tablet. This thready discusses how to launch the handwriting app that you install on your Android using ActivityStarter. Activity starter to launch google handwriting input
Yes, it might be used to interpret a handwritten A to a but you will have to figure out how to interface the google tool to your App Inventor 2 app.