MacOS – Programmatically catch app opening / closing

You can do this with Automator. Open Automator and:

1. Create a workflow
2. Add a “Find Calendar Items” action and add it
3. Change the first line from “Find events where:” to “Find reminders where:”
4. To grab all the reminders change the “Any Content contains ______” to “Title is not ______“ and leave the text field empty. You may need to change to fit your needs better.
5. Then add an “Event Summary” action underneath it.
6. From here you can use Automator to do whatever you like with the reminders.

To help you test it out, use a “View Results” action. You can insert it anywhere and it will show you what the output of the prior action was.

For doing this from Terminal:

1. Find the .workflow file you saved and copy the path to it.
2. Run automator and pass in the path.
3. Now you should see the results or errors of running the actions.

You will need to run this manually once to enable Terminal to prompt for access to your Reminders.

See also: Automator: Find Reminders by list?

Sounds like ControlPlane might be the app you're looking for.

With this utility you can define different contexts based on various criteria (i.e. Wi-Fi name, attached peripherals), and execute tasks upon entering or leaving these contexts.