I'm guessing the average phone size is about 155 square centimeters, or 1.5% of a square meter. Multiply that by 3 Watts, and you get 200 Watts. That's about 15% of the suns energy per unit area. Of course it's probably a different type of radiation, and the whole phone isn't going to be radiating, so the intensity might be stronger.
The way to measure this is based on distance. If say a phone emits 3 watts of RF but it’s set 1 meter away the area that 3 watts operates on is 4pi1^2. If the 3 watts is being emitted right next to you then maybe the size of the antenna stars to mater. This is why if your really worried about RF using wired headphones and never taking a call with the phone pressed up to your ear is the best thing you can do
