The chore wheel [1], which my wife and I used to run on an old iPad to track evening chores. It uses local storage for recurring chores and one-off reminders. We tried a bunch of other tools but they were all too full featured or slow to ooperate. It replaced a paper list.
When debugging network issues I realized I was going back and forth between my computer, router, and cables under the desk. I created an audible network check [2] so I could just listen to hear the status.