Dyamic form based on third-party API

A form field which fetches from a third-party API after it has been filled in.

One use case would be a form field which searches through Unsplash photos after the field has been filled in.

An example of this particular form would be this video:
https://algo.tv/includes/projects/Nextatlas/nextatlasScreencast.mp4

Would love to know how and whether that is possible!