Looks interesting, though on recent iOS devices, images will be in HEIF format, which is about 50% the size of JPEG at similar quality, and MozJPEG isn't compatible with it afaik.
If you're interested in compressing JPEGs without quality loss, there's a free Mac app called ImageOptim that can handle JPEG, GIF and PNG. It has Google's Guetlzi, so on some JPEG you can reach 20-40% compression without any loss of quality that I could detect (and sometimes lower levels around 10% on images that are already well compressed or smaller resolution).
If you're interested in compressing JPEGs without quality loss, there's a free Mac app called ImageOptim that can handle JPEG, GIF and PNG. It has Google's Guetlzi, so on some JPEG you can reach 20-40% compression without any loss of quality that I could detect (and sometimes lower levels around 10% on images that are already well compressed or smaller resolution).
https://imageoptim.com/mac