Keeping your cell phone anywhere near your heart is a really really bad idea health wise

Why?
If you actually read your fine print in your instructions when you buy your cell phone it says something like: "Don't wear your cell phone next to your skin because it could burn your skin".

So, the problem becomes that people DON'T READ this stuff and so will do almost anything with their cell phones including put them on vibrate and leaving them near their genitalia.

Which is a really really bad idea if you ever want to actually have children. Because it is quite likely "At least regarding sperm cell production" that your cell phone too near your genitals likely also kills Sperm cells. It could affect your ovaries if you have those too by the way. So, if you are a woman and carry a purse likely you would want your cell phone in your purse away from your body if you want to get pregnant and as far away as possible from your head or genitals, especially if you want healthy children.