Two very very deep rabbit holes in the last 6 months:

- Designed/built a small USB controlled pan/tilt camera head to control the mirrorless I use as a webcam (couple of servos, gears, belts), and then designed/built a custom ortholinear keyboard with a joystick to control the camera (custom PCB, CNC'd aluminum case, etc)

- I'm a pretty big runner, built my own web based calendar UI that integrates with Google Calendar where I can type in workouts like "1 mile warmup @z2 + 5x(30 seconds @ 6:00/mile + 0.5 miles recovery) + 1 mile cooldown" and this gets parsed/total weekly mileage gets tallied. The next step down this rabbit hole is building a small iOS app to automatically generate Apple Watch Workouts using WorkoutKit.