Somehow I think the smartphones and cellphones are pretty safe but I hardly every talk on them. Mostly it seems like I use them for text messages and taking pictures. I've heard that the EM radiation from them can be an issue though. There are even some studies that seem to indicate that the signals from phones are harmful to bees and putting a cellphone into a bee hive will prevent them from coming back to the hive properly. (Maybe you should search the web on this if you are interested, some of the details of the study I might have gotten confused over)