There is no example for this yet so, so I made my own. The first attempt works but the map does not refresh after the marker's location is updated. Thus leaving a ghost marker behind until the map cache gets refreshed, which happens upon zooming. This can be remedied if there is a way to force refresh the loaded map.
However, I think a better solution would be to access displayed markers from the CartoDBLayer. There does not seem to be a clear way of doing this. Is there?