Body energy harvesting system

Non-sustainable, limited electric power sources (power banks, etc) and non-portable ones (power outlets) to charge our on-the-go electronic devices (cell phones, wearables, etc).

Our body is a source of electrical power, in very small quantities, but it is, e.g: heart, brain, muscles, etc. So the idea is to develop a "device" that is capable of gathering all these small amounts of energy (electrical current) and store them for getting a portable and everlasting source of power.