What’s being promised here appears to be a web app, so it will work in a browser with the SAFE plugin, and will be written in HTML/CSS/Javascript (like SAFEpress).
So the process of building this kind of app is fairly straightforward. The tricky part is that you’ll be talking to SAFE network rather than a web server (which will be the same for all SAFE apps).
It is though likely that this early plugin will offer a subset of the SAFE API, but we’ll have to wait and see how much they expose.
EDIT: The diagram in this SAFEpress post shows how I believe web apps will work on SAFE Network.