Add percol and fpp.

README.md

@@ -115,6 +115,10 @@ Scope:
       stat -c '%A %a %n' /etc/timezone
 ```
 
+- For interactive selection of values from the output of another command, use [`percol`](https://github.com/mooz/percol).
+
+- For interaction with files based on the output of another command (like `git`), use `fpp` ([PathPicker](https://github.com/facebook/PathPicker)).
+
 
 ## Processing files and data