The radiator is your phone. The wireless headset does a lot of receiving and very, very little radiation. That's why those tiny bluetooth things can have many weeks of battery lifetime on a battery the size of a fingernail: They don't radiate much energy either towards your brain or towards the phone.

(Digressing, I wonder how much radiation incidental WLAN use on a phone causes, compared to a bluetooth headset. I mean things like googleplay chancing to upgrade a few apps via WLAN while you're holding the phone against your ear.)