Although there has yet to be any fully conclusive evidence that smartphone radiation is bad for fertility, you might want to consider a pair of Spartans. As well as having an awesome name, the French brand of underwear for men are specially designed to block the radiation from phones; a key issue if you keep yours in your trouser pockets.
But, as we said, there isn't any solid proof to say that smart and mobile phones are dangerous, or that they adversely effect male fertility. Still, the radiation is still there, albeit in the form of WiFi, Bluetooth, and the actual broadcast signal from you network provider. So if you had a chance to keep your chestnuts in pristine condition, would ya?
Buy hey, as fancy as they look, they're still going to set you back around $50 a pair. A pair!