I posted yesterday that it is fairly easy (with low level opsys access) to program a cell phone to modulate its output 4-30 Hz by shifting the output signal strength (the "bars").
Since the RF energy drops by 1/x^3, I suggest everyone charge their cell phone at night at least 3-4 feet away from their head. Across the room is better. Think about it. At night, when hooked to a charging cable, the cell phone can be set to max transmitted power without causing the battery to drop.
I have decided to use my land line more and to use a non-Bluetooth wired headset, with a 6 foot extension cable, for my long cell phone calls.