i make an effort not to even leave my phone lying around either a) my head or b) my tummy....
i don't care what anyone says, mobile phone use is a major factor in the huge increase in brain tumours.... i try not to use mine too much and i certainly wouldn't be actively putting it anywhere near my tum....

have you read what Dr Charlie Teo, leading nuero-surgeon says about mobile phone use..... i'm going to listen to the nuero-surgeon....

personally i think its like a few decades ago when cigarette companies told us cigarettes aren't dangerous.... just the same.