I have a car charger for my phone, but I frequently forget to use it. I end up with a dead cell phone and annoyed loved ones. I wanted to come up with an idea that would PASSIVELY charge my phone while driving and without having to remember to remove it from my pocket.
Have you ever built a diode
radio? It powers the ear piece entirely with the power extracted from the radio waves. Have you also seen the early un-tuned radio experiments involving large coils of wire mounted on walls?
I propose a receiver built into a cell phone tuned very precisely to a currently unused radio band. (It wouldn't matter if the band gets interference; it would actually be desired at times.) Mounted within the consumer's vehicle, a matching transmitter would be mounted broadcasting on said frequency in order to charge the consumer's cellular telephone.
The first obvious criticism may be of health concern, but a proper radio frequency may be chosen to alleviate such concerns. This idea need not use radio waves; pure magnetic fields might also prove useful albeit harmful to credit cards.
The second obvious criticism may be that such a device would be inefficient, but with the lower power consumption of cell phones, I believe an efficiency of 5% would be perfectly acceptable. The device could perhaps locate the phone's position within the car (via triangulation of the receiver's heterodyne) and focus the energy toward it.