A phone app that detect you are driving and stops your phone from ringing to avoid you talking on phone when driving.
Ammunition Manufacture should invent a projectile so when you shoot a wild animal from a long way a way you could mark the spot where you shot the wild animal. Similar to a tracer from the war but this would have paint to mark the spot or near to where you thought you shot a wild animal.
A good way to stop getting indigestion and its free. Sometimes the main reason we can get indigestion is we eat and drink too quickly. Try eating slower and see if your compliant goes away. But of course, if it doesn't you should see your doctor.