I am not aware of any widgets that currently accomplish this.
If you are looking to use an API I would start by looking at Amazon Rekognition which already has a level of mendix support through the Amazon Rekognition Connector. There will be some additional challenges to ensure that it works well on Native Mobile.
Another route you could look into would be leveraging a react native package. Liveness-detection-react-native and react-native-face-api both look promising, although I haven't implemented either of them.
Whichever approach best fits your use case and development strengths would be the route that I suggest you take.
Hope this helps give you some direction!
Let us know how things go for you either here or on the native mobile slack channel!