I don't know what I'd use this for, but the pictures are hitting that part of me that loves grayscale Palm devices really, really hard.
In fact, this comment made me remember that I’ve had a color filter accessibility setting in iOS that lets me turn the screen to grayscale.
Kind of a trip to use a modern smartphone like this, but also kind of… relaxing in a weird way.
Settings -> Accessibility -> Display & Text Size -> Color Filters
You can even set a shortcut to quickly toggle them on and off.