Anyone who has been at sea or has simply become lost hiking in the woods (before the satellite age) knows the importance of a compass, an ancient device which works on the principles of magnetism. A compass is a magnetically sensitive device that is capable of indicating the direction of the magnetic north of the earth's magnetosphere, or regions dominated by the magnetic field of celestial objects.
This device was invented in China in the second century, A.D., and was used for navigation by the eleventh century. By 1300, the dry compass was invented in Europe; this compass has been replaced by the liquid-filled magnetic compass of the twentieth century. A gyrocompass or an astrocompass can be used now to find "true North" since it is unaffected by magnetic fields, power circuits which may be nearby, or close masses of ferrous (iron) metals.
Don't forget about MRI (magnetic resonance imaging) machines.
Obviously MRI's don't directly affect our lives every day (unless we are sick or have a sick/hurt loved one) but the fact that hospitals have these devices certainly affects all of us. This means that several ailments, injuries, and sources of unknown pain can fairly easily be seen and treated.
I mean, MRI's are used for locating tumors all the way down to seeing if a person has a slipped or ruptured disc in the spine. Lots of people have MRIs after a sports injury to see if surgery is necessary. And basically, all an MRI machine is, is a giant magnet.
There's one that is a pretty integral part of my life many days, but may not be for everybody. I have a little tiny magnet attached to the wheel of my bicycle, actually one of them is attached to the wheels of several of my bikes, and as it rotates past a sensor on the fork, it gives me speed and cadence data that I use to get an idea of what I am doing and sometimes to compare it to what I have done on other days, etc.
I also have to say that I think the magnet in the remote that sticks onto the side of my imac is a pretty sweet little use of a magnet as well.
I do not know if this counts in your opinion for something that "uses magnets," but to me, the most important device that uses magnets is an electrical generator. Generators pretty much all use magnets and coils of wire to produce electricity.
I cannot think of anything that affects our daily lives as much as electricity. We use it to light our homes and keep our food cool in the refrigerator. When it comes time, we (at least in my home) use it to cook. We use it to power our computers, to make our water hot, etc.
All of our electricity comes from electrical generators that use magnets as a way to create the electric current that we use.