I would guess on the fly optimizing for mobile/etc devices, shaving up to 100s of kilobytes off page sizes in a best case scenario - zoomed right out where all

I would guess on the fly optimizing for mobile/etc devices, shaving up to 100s of kilobytes off page sizes in a best case scenario - zoomed right out where all the images are really tiny, without the delay of having to wait for them to fetch the completed file first. Another interesting approach would be to not only resize them like the guy's doing but to patch it all together into a spritesheet along the way - on the fly transformation of 30 requests/120kb of images becoming a single request for the shrunk down, merged version. Even outside of mobile it could "speed up the web" by optimizing & resizing uncompressed or resized-in-html images everywhere. It sounds like it has some really interesting applications.