The September 19, 2012 article suggested using iDisplay to turn an older iPhone or iPad into an additional display for a Mac or PC. The saved page linked to getidisplay.com and App Store ID 363500805, with a demonstration credited to Connectify.
This is a historical software use case. It does not verify that the original app, companion software or wireless setup works with a particular device today.
Give the extra screen a defined job
A second display is most useful when it has a purpose. A reference document, a status view or a small set of notes may suit a compact screen differently from a window requiring frequent precise interaction.
Decide what you want to keep visible before investing time in a setup. That makes it easier to judge whether the extra surface actually reduces switching between windows.
Check the complete pairing
A phone-side app is only part of a display-extension system. The computer, companion software and connection method must work together. A successful installation on one device is not proof that the full pair is compatible.
Current requirements need to come from the developer’s documentation for the exact versions involved, rather than from this 2012 suggestion.
The restored article preserves the original reuse idea and the iDisplay identity. It does not replace the app with a same-name product or promise that every old phone can become a useful extra screen.