Without dismissing all crypto currencies this seems more immediately practically useful:-)
https://paragonie.com/blog/2016/10/guide-automatic-security-...
https://paragonie.com/blog/2017/07/chronicle-will-make-you-q...
I've written a lot about the design and utility of append-only cryptographic ledgers for this use case.
Mozilla has their own implementation based on Certificate Transparency: https://wiki.mozilla.org/Security/Binary_Transparency
Filippo Valsorda is working on bringing something similar to the Go ecosystem, based on a Trillian personality.
There's a lot of work going on, there's just not a marketing team behind these efforts, so you only ever hear about blockchains and ICOs.