In this clip we will see that iphone emits Radio Frequency (RF) Electromagnetic Radiaiton (EMR) in various modes, even when not in use, even when idle!
Using a Smart phone you can stay connected all the time, using email, Internet, applications, text msg, and games. But did you know that during all these activities, and sometimes even when it appears to be idle, your smart phone transmits and emits RF EMR?

In the following video please pay attention to WHEN and FOR HOW LONG the iPhone emits RF EMR.
As this video will show , the iPhone, as every smart phone, emits RF EMR even when you are not using it as it synchronizes to the network. The length, level and frequency of the transmissions depend on the smart phone's configuration and usage. For example, if you have lots of widgets and applications installed on your smart phone it will transmit more often.
So, if you want to limit your exposure, turn off 3G and WIFI communications when your are not using them. Better not use a smart phone at all.
Please take this into consideration before buying your child a smart phone.