Useful to have a special mode for sha256sum output that built a tree of the hashes, and allowed for later extraction - not unlike Git tree mode.
Should be able to specify a digest to timestamp, rather than being limited to timestamping files.
Probably best to add a way to get headers from calendar servers + other sources, then check PoW. Also need to improve docs re: using a pruned node.
Explain requirements for running a pruned Bitcoin node - it's really not as big a deal as people think!