Hi Erik,
There is no widget for this, but there are various online services that you can use for this, for instance Watson's text-to-speech service: https://www.ibm.com/watson/services/speech-to-text/
EDIT: While replying I thought of this you can use: in the Appstore is the Watson connector suite: https://appstore.home.mendix.com/link/app/2860/. I would download this if I were you and go from here!
Im not sure if the Watson connector can do speech to text but it is worth looking into https://appstore.home.mendix.com/link/app/2860/Mendix/IBM-Watson-Connector-Suite