I've seen similar devices at Walmart and other stores. Never used one. I'm not even a fan of 'crock sticks' or the Sharpmaker.
Obviously, the investment to try the device is small.
Fixed-angle of 40 degrees is an obvious drawback for general versatility, but I think these little tools might be ideal for quickly reviving edges for a fisherman's filet knife, since thin blades slice well even with relatively blunt edge angles.
Even when the ceramic inserts clog with metal, they would seem to serve well to at least align the edge of a filet knife.