Ideas

A phone app that reads the numbers off a basic bathroom scale and saves them for you

Some bathroom scales flash weight, BMI and body-fat readings on a small screen one at a time, so copying them into a spreadsheet by hand is slow and easy to get wrong. A simple phone app could watch the scale's screen through the camera for one full round, read each number, and save them in the same order every time. It could then copy them straight into a spreadsheet, and get better at reading different scale models over time. It would only copy the readings down, without interpreting them or giving medical advice.

Asked for by a poster on Software Recommendations Stack Exchange

A random-interval workout timer you can load with your own exercises

Enter exercises (jog, walk, sprint), a set of possible durations, rest time and number of rounds, and the timer picks each round at random. Keeps interval training unpredictable without planning every block. Audio or vibration cues tell you when to switch.