I bought this device to detect the radiation at my home, but despite it being named "cell sensor", I was unable to detect the cell phone signal from my iPhone 3G. I followed the direction, did the 90 degrees and 8 inch apart as described in the manual, put the probe next to the sensor, put it on the sensitive setting, and... detected nothing. Then during a call, I tried moving the cell phone in all angle combinations... nothing. I thought I had a defective unit, so I requested a replacement, got another brand new unit, and did the exact same thing. Nothing... the needle stays around 0. Same goes with wireless mouse and baby monitors. How do you make a "cell sensor" that doesn't sense a cell phone is beyond me.
On the other hand, this device works well detecting EMF from appliances such as refrigerator, microwave, lights, etc. Not sure it has really helped me avoid EMF energy other than confirm there's EMF emitting from electronic devices, and to stay 6 feet away from the microwave, but otherwise the level is so low typically that there's really not much that needed to be addressed.
If you plan to get this to detect EMF, it seems to work well, although I have nothing to compare it against. On the other hand, if you want to get one to detect wireless radiation, forget it.