There is an another fun useful application of the piezoelectrical phenomena.
Lets take a look at common shoes. They commonly use elastic soles for a dumping moving effect during walking/running.
Imagine the same shoes, but with piezoelectric elements on its sole (just same as in the piezoelectric lighter) with the ability to produce charge at any type of tension – compression or stretching.
Along with dumping effect they will produce a lot of electricity when moving, which can be gathered and collected lets say in attached accumulator and used for example for charging phones and devices, lighting, etc.
For more discussions on this topic – take a look at stack physics