Jog measures the impact force on your knees when you go jogging and warns you if the force is too high. This means you could be damaging your knees, leading to problems in later life.
This app can help you develop better running form, making your footwork lighter, by running up on your toes more, thus reducing the heel strike force, knee impact force and hip loading force.
Jog uses your phone's accelerometer to measure how heavy you are on your feet and estimates the impact on your joints - while this depends on the type of phone you have and where you put it (in a loose/tight pocket, strapped to your arm, etc), it can be useful to see if you've got a habit of bad running form and remind you to think about correcting your form to reduce wear and tear on your joints.
Happy jogging 🏃