Don't forget that a cellphone automatically reduces its transmit power when it is close to the cell tower.

So in a built-up area with many cell towers you will be incurring much less radiation from your phone than in a rural area where the phone may switch itself to full transmit power.

In any case, 90% of my cellphone use is in conjunction with my N810. I don't even need the cellphone to be near my body, and I'm presuming that the bluetooth radiation from the N810 is sufficiently lower in strength that I don't need to worry about it.

Regards,
Roger