(American Chemical Society)

A new kind of temporary tattoo may someday let you power everything from your Fitbit to your iPhone using your body’s own sweat.

Developed by researchers at the University of California, San Diego, the tattoo sticks to your skin and measures the amount of chemical lactate in your sweat, and then uses that lactate to create a small fuel cell.

The tattoo was originally designed to improve how doctors check patients’ lactate levels, a process that currently requires a blood test. But researchers wanted to see what else they could to with the tattoo. According to the American Chemical Society, a sensor in the tattoo pulls electrons from the lactate, which generates an electrical current. Researchers added a battery to the lactate sensor to capture and store the current produced by the patch, creating what is called a biofuel cell.

The general idea is that the more you sweat — whether it be from a long bike ride or a walk to the fridge — the more lactate your body will produce, which increases the amount of electrons (power) the battery can capture. (Finally, some good news for excessively sweaty people!)

Right now, the patch can create only a minuscule amount of power, though the team from UCSD hopes that this biofuel cell will one day be able to generate enough juice to power smartwatches, heart-rate monitors, and possibly your smartphone. And with Motorola having created a temporary tattoo that acts as a password to unlock your phone — well, the next must-have accessory for your iPhone might just be a little body ink.

Email Daniel at dhowley@yahoo-inc.com; follow him on Twitter at @DanielHowley or on Google+ here.