I paid $3.97, so was not expecting space age technology.
The four functions are
1. A whistle that I can whistle louder than without the whistle.
2. A microscopic thermometer.
3. A compass, likewise Lilliputian.
4. A magnifier that swings out from the innards but you could not use it to read the compass or the thermometer.
So this combination is so I will know how cold I am when I am lost and where north is from where I am lost and the whistle to summon help when the rescuers are almost stepping on me...
@Mamapolo2016 if it magnifies than yes , even water in a clear plastic bag can be used as a magnifier for sunlight to pass through and start a fire , saw this somewhere