A wireless showerhead is clearly impossible… if you don’t have a machine that works on very little energy and somehow was able to store enough hydrogen while also sucking in oxygen to make water

Say we had technology so efficient to make thus process possible, to make 1 liter of water (1 kg) you just need 1/9 of a kg of hydrogen, so if your showehead stored 1 kg of hydrogen in an extremely enclosed space, you could "pull 9 liters of water out of the air

Even if this device was possible, it would be extremely impractical, and would probably suffocate you by sucking all the o2 out of the air if you are in an enclosed space