I recently used the Rest API in conjunction with Advanced Custom Fields and a plugin to utilize acf through the Rest API as well. We needed a dynamic way for our client to add custom post types that appeared on a Google Map as they were added. Here is the website currently using it: http://findartdoorsrva.org/.

It was a fairly straightforward process, call the endpoints via an ajax request, loop through the data objects that were created, and then build out objects using the Google Maps api. Now whenever a new door is added or updated, the map data is updated as well. When you click on the door icons, it displays all of the post/acf information.

All in all it was a really fun project and a perfect opportunity to try out using the api.