follow search

 follow search  is a reader search feature implemented by at least Twitter that similar to follow, shows new posts in the reader that match the search criteria, independent of author.

IndieWeb Examples
No known IndieWeb Examples.

Twitter
Starting around 2017-08-25, Twitter introduced "Follow search" as a button and UI prompt to some users.

Screenshots:

Stay Informed prompt
When first shown to the user, a UI prompt is provided that explains the feature a bit and provides multiple "Follow search" buttons:

Hashtag follow search UI prompt - from https://twitter.com/hashtag/newbase60



Conditional OR follow search UI prompt - from https://twitter.com/search?f=tweets&vertical=default&q=newbase60%20OR%20newbase64



Follow Search button
At some point the UI prompt no longer shows up on search results, leaving only the "Follow search" button near the top - from https://twitter.com/hashtag/indieweb?f=tweets&vertical=default



If you click the "Follow Search" button it is inverted and turns into a "Following search" button:



Hovering over the button turns it red and changes the text to "Unfollow search"

follow search webaction
In a system where different services perform posting, search, and reading services, "Follow Search" would make sense as a webaction that a search service could provide that the user's browser could delegate to their preferred reader service, perhaps on their own site.