You can't get much more environmentally friendly than a battery charger that could theoretically power up your smartphone with sweat and tears.

Enter MyFC's Jaq fuel cell charger. Not only is it the smallest battery pack of its kind, it also delivers mains-free energy to your device via salt water.

It produces charge through an internal PowerCard, a sheet of salt and water that generates hydrogen power through a chemical reaction.

Reacting chemicals are probably the last thing you want anywhere near your smartphone, but MyFC insists the Jaq is both safe and eco-friendly.

The startup has just given the accessory its European debut at the Mobile World Congress in Barcelona, but a release date for the UK and other markets on the continent is yet to be announced.

If the promise of green energy, chemical reactions in your pocket, and ultra-portability have piqued your interest, the Jaq is available to pre-order on the company's website.