Della has a rare genetic condition called Bainbridge-Ropers Syndrome which affects her ability to speak.
Her brother, Archer, wanted to help his sister communicate – and didn’t think it was fair to rely on expensive communication apps.
Aged just 16, Archer decided to develop one himself, for free and accessible to all.
Produced by Harry Bligh and Dianne King.
This article was originally published by Bbc.co.uk. Read the original article here.