Bio-electronic device can produce electricity using nothing but humidity

400W/m^2 would be awesome. Unfortunately, as szielins points out in the comments it's quite a bit less:

"The devices produce a sustained voltage of around 0.5 volts across a 7-micrometre-thick film, with a current density of around 17 microamperes per square centimetre." From P = IV, that's .5 V * 17 x 10^-6 A / cm^2, or 8.5 microwatts per square centimeter, or .085 watts per square meter--much more reasonable.