Yay 
Definitely one of the first – we’re running a limited trial right now to check everything works well. In terms of things built on the API, check out @rdingwall’s amazing canonical list of projects: https://github.com/rdingwall/awesome-mondo, as well as this list of API wrappers: Community supported API wrappers. There’s also a couple of other projects found by searching on the forum: https://community.monzo.com/search?q=api Lots more to come and better discovery of projects soon 
Hope that helps! Please keep us updated on how the card goes and feel free to ask any questions