You could use this library https://github.com/szimek/signature_pad.
I am going to attempt to use it and possible wrap it in an angular 2 direction component.
I’m working in other project by now and I will return to this project in the future.
One possible solution is to install a drawing app in the device, and make a intent to the drawing app, so that the user draws in the signature in drawing app, and waits the drawing app to return an image with the signature to my app. Perhaps it must be the most effective option if the drawing app is a native app.