Depends on the environment and collector area. Might be OK for a separate charger, but I'd be surprised if it can be put in a handset and provide sufficient amounts of power.

Thermal harvesting has it's issues. If you want a lot of power, it will feel cold, really cold. Second, the body adapts, so after the initial surge, your body will try to preserve temperature and thus less power. There are of course parts less susceptible, but those generally arent places you want to have your gadgets Also, you might not want a radio source right on your skin most of the the time.

Solar (unless directly exposed to the sun) PV gives very little power, especially if you consider these devices spend their time mostly indoors or in pockets. A tiny fm radio might get away with a few mW, but we need more (and we need it constantly).

Considering we're talking mostly about devices you have on/with you, Gerbick/Texrats kinetic energy recovery suggestion does make sense to me (with the presumption that your not a mega-couch-potato) - IF the uneven kinetic energy input can be converted to electrical energy in an efficient way (watches are again at an advantage as they need really tiny amounts of energy).

But the OP is correct - the issue is not not getting power from the environment, it's that it's too little/too unreliable to effectively use for charging batteries with current technology.