In my family home growing up, me and my sister had our bedrooms upstairs while the dining/living rooms were downstairs. When it was dinner time, my mother would yell out "Dinners ready!" up the staircase - often to deaf ears, as us young teens were pre-occupied with loud music, gaming or talking on the phone.<p>After coming down one-to-many times to a cold dinner, I developed my first "app" with MIT App Inventor - <i>Dinners Ready</i>, an app with three buttons: "kid A", "kid B", and a larger "Both". Pressing a button would send a simple text message saying dinner is ready.<p>My mum <i>loved</i> it. Suddenly she didn't have to worry about fruitlessly yelling to her distracted kids. I wouldn't have to rely on my grumbling stomach to come downstairs to an empty dining table with my food going cold. We used it for years, and she still brings it up from time to time. To this day it remains my most well-reviewed app with 100% happy users.