Computer Vision - Eye Contact
Train a computer to recognize eye contact - i.e. whether a person is looking directly into a camera. Use this to drive interaction with the computer (e.g. find "good" photos from a set of images, take a photo when eye contact is made, trigger a voice assistant, etc).
Personal Trainer, a la New York Times Seven Minute Workout
Develop an application to run through the NYT Seven Minute Workout. Expand the list of exercises, and add variability/randomness to the workouts, to yield a simple, virtual personal trainer.
Open Source Adventure Course
Make a game that teaches the player to program/teaches them various algorithms. For example, the player could use basic flow of control to solve puzzles/riddles, defeat enemies by implementing a sorting algorithm that works faster than theirs, or race through a world using an algorithm such as A* to plot their course.. Publish the game under and open source license so anyone can add puzzles, levels, worlds, etc.