Display and handling for applications that have stopped responding.
- Explain what is happening to the user.
- Let the user wait, or allow them to kill the app.
- Communicate that the system is doing the error handling, and not the app itself.
- Ideally enable problem reporting and other diagnostics for the cause of the unresponsiveness.
iOS just kills apps if they stop responding for too long, without any special UI being presented; from the user's point of view, the app has just crashed due to a bug in the app.