Unfortunately you can't use NoteDex (or any 3rd party app) on the Remarkable device. The Remarkable device is a proprietary operating system, unlike the Boox range of devices that can run Android. At this time we don't think the Remarkable device supports using a web browser - if it did then you could use NoteDex on the web.
NoteDex can run on any Android powered device, and of course any Web, Windows, Mac or iOS device also.