A bluetooth works on frequentie 2.45 Ghz, Gsm on 800-1900 Mhz, FM radio signals on 80-108 Mhz. But still the frequentie doesn't affect you, if it's 50 Mhz or 2,5 Ghz, it doesn't matter, our own sun transmits more signal that this...
It's the amount of RF energy that you expose that makes if a phone/headset 'dangerous' (called SAR rating. it's allread 'proven' that analogue phone can cause cancer, but also transmit a lot of SAR.
For GSM the limit has being set on SAR 1.6 W/kg. Some cell phones, like the Nokia 6230 has only got 0.59 W/kg while the 3310 has got 0.96 W/kg.
More extreme cases:
Samsung P400 1.18 W/kg and the Motorola V3688 only 0.02 W/kg...
If you take now the SAR level of a bluetooth headset it's around: 0.1 W/kg, which is not a lot...
here is more information if you want to know the sar levels and more reference
http://www.bemi.se/founder/clips/cellularSAR.html