This is a interesting discussion, despite there are no proves that wi-fi its not safe... wifi routers uses so low power that in 20 m and a wall,signal is gone.
Myself already serched about problems on wifi ,before have wi-fi and use wireless arduinos(nrf24..) ,but know i think its senseless.
before of all you shoud read how this "world" works. because compare nrf24l01 card with wifi is like compare a bicycle with a car...
on temperature sensor for example ,each command activate the card for milisenconds and sleep again during 10 minutes (in my case).
i guess put your head in to the sun makes more dammage and get more radiation thant this....
