It uses the geo-location function found in modern browsers to give an app-like experience in the browser. i.e. no downloads, no sign-in (or sign-up) to an app store.
If you add to your homescreen it should also look like a conventional app.
Works across devices as the browser is the platform not the device (challenge is to make it work across browsers of course). Downside is needs user permission (which may be turned off globally - deep within their settings somewhere - so I may ultimately need a conventional app anyway).
Anyway. If you can try it and provide feedback I would appreciate it!