I love fictions, especially science fictions. One particular kind of those science fictions is called 玄幻修仙 (Fantasy Xiu Xian). In these fictions, people absorb energy from the space/air and turn it into a form of power stored inside the body. Once that power becomes large enough, we either explode due to capacity limits of our body, or we successfully compress those power into a core called (金丹). And beyond it, there are many other levels with higher power density and more power.
Such abstract idea of power can be considered as bioelectricity. I am no biology experts, but I always wonder why we cannot leverage these power generated from our body to boot up electronics.
Doing so can improve our life without worrying about batteries. We never worry if our cellphone or smart watch is not charged. Depending on the power our body can deliver, we may enable lots of wearable devices. Doing so may also give disabilities a new form of their original sensibility.
The alternative solutions are, for example, wireless charging and bringing a portable power bank. Both have very lower conversion rate (input that "stores" energy to output that charges our device).
Maybe this will become true sometime.