This has been similarly discussed before. Maybe even discussed directly by someone else.
Obviously fat fingering your signature on a device screen isn't the greatest representation of your true signature.
I've always had a Samsung Note so I've always been able to use the built in S pen but it's still somewhat of a nuisance repeatedly signing documents. Sometimes I have 24 or more documents to sign in my queue.
I go through the app, get to the point needed, pull out my pen, then put it away, finish the app and submit. Then repeat 23 more times...
I think it would be a nice option to take advantage of smart device finger print reading technology.
If a signature image could be stored and unlocked by scanning your finger print that would be a great feature.
Adobe does something like this (meaning stores a digital signature image).