Source: https://github.com/doubleblacksoftware/simple-weight-tracker

The Simple Weight Tracker is a simple, but effective way to track your body weight from day to day. If you need a simple weight tracker without all the fluff, advertising, and social network integration, try this app.

To use, tap the "add" button (bottom right corner) and enter your current weight, or weight at a different point in time. Tap "add now" or "select date" to select a different date than today. That's it. The weight tracker will list your weight and the date it was entered. To get an idea of how your body weight is changing over time, switch to the chart tab to see a simple line chart of your progress.

It doesn't get much simpler than that!