This term describes agents which passively retrieve and display useful information based on a user’s action.
For example, the Remembrance Agent is an Emacs extension which looks at the contents of the current document (near the cursor?) and finds associated documents, email messages, etc which are similar.
Margin Notes is an agent which annotates web pages with links to personal files which may be relevant.
Related: Peripheral vision
Rhodes, B. J., & Maes, P. (2000). Just-in-time information retrieval agents. IBM Systems Journal, 39(3.4), 685–704. https://doi.org/10.1147/sj.393.0685