How does this improve on a pipe like: "dd ... | md5sum" (or sha1sum, etc) ?
It appears "the ability to compute multiple message digests with one pass of the source data" would be it. If so, to eliminate code duplication and resulting maintenance, wouldn't it have been better to create a pipe "splitter" that would accept the data on its stdin and launch the appropriate digest tools and feed all of their stdin the same data?
An open, cross-platform journaling program.
A scientific plotting package.