Use your phone as weightlifting. You can add the additional weight of the arm (and register it on the app). You register phone brand, additional weight and the number of rounds to lift. The App will provide an animation when you lift and lower the phone, and count the number of rounds of specified weight. When you have reached your goal, it will presente the results with a total weight lifted.
A fun little app that can be used anywhere (e.g. the office).
Ok