Mass measuring/estimating without a scale, with your mobile phone? Yes it is possible. The elastic collision in physics means that two object collides and bounce off each other. In physics we calculate it with the law of conservation of momentum and conservation of energy. This equation system is able for show the unknown mass of the object what participates in the collosion event.
The process is the following. Install the Mobile Scale app on your phone, type known target mass to estimate the mass of your phone(calibration), and when the LED is on, perform a little and careful elastic collision between the phone and the object. if the mass of phone is measured (estimated), the unkown mass measuring can be performed with same process , when the LED is on, perform a little and careful elastic collision between your device(phone) and the unknown mass.
The author is not responsible for damage to the mobile, so please wrap your device carefully before calibrating/measuring. Children should only use the app under parental supervision.