I'm going to expand the definition of "daily life application" from things you actually use daily to things you experience daily. These could be engaging too!

For example... what are sunspots? How does the plumbing around your house work? How does a car battery work? How does a microwave oven work?

Another thought. If we are unable to find applications for a technique, should we place such an emphasis on teaching it? I look around and see all the very practical (and interesting!) math and science that is not being taught, e.g. signal processing, just because they are nontraditional. It's a shame to me.