If you review the TTField information, you can see that the fields these devices emit are much stronger and at lower frequency bands. For instance, a smartphone held 5 cm away emits roughly 0.025 V/cm, whereas the helmet we're discussing hits you with anywhere between 1.0 and 3.5 V/cm. So the lower band is about 40 times stronger than a smartphone held against your temple!
Wireless headphones emit 10-400 times less energy than smartphones do. My personal takeaway is that you're safe.
3 orders of magnitude of margin in terms of power is still way less than I expected, considering that I have these devices on my head for 3 order of magnitude more hours than people using that treatment.
Of course there are dose effects and non linearities so we should very very likely be good. But huh.