This company is marketing a product which uses the photosynthesis of a single houseplant to charge a phone.
IIRC the theoretical maximum efficiency of photosynthesis is about 10%, so at best the plant would be able to act as a solar panel with 10% efficiency. I would think, however, that much of the energy used by the plant is for growing. I do not see how they are accessing energy from the plant without (for example) burning it.
Not impossible, but highly unlikely
The technology described does exist. Scientifically this is called Plant Microbial Fuel Cell. However Bioo's claims of 40 W/m² seem greatly exaggerated.
People involved in e-Plant, a Dutch company which already has similar product on the market have published a number of scientific papers in Biotechnology for Biofuels journal. Most relevant one is "The flat-plate plant-microbial fuel cell: The effect of a new design on internal resistances", which talks about improvements in efficiency, which are still nowhere near 40 W/m².
With the flat-plate design current and power density per geometric planting area were increased (from 0.15 A/m2 to 1.6 A/m2 and from 0.22 W/m2 to and 0.44 W/m2)as were current and power output per volume (from 7.5 A/m3 to 122 A/m3 and from 1.3 W/m3 to 5.8 W/m3)
As for question if they plant in pot would be able to charge cell phone, for example iPhone 6+ has 11.1Wh battery, charging losses on Li-Po batteries can be neglected.
Giving a Bioo very generous benefit of doubt, and assuming that they did something revolutionary to bring that to do 20 W/m3, such a flower pot might generate 100-200mW. Which would take 120-60 hours to charge iPhone. So it's not really feasible even with generous assumptions in their favor.
