I have a fitbit and I love it! I am wearing it now as a matter of fact! I use the sleep tracker and it has helped me identify and fix problems with my sleep cycle / awaking times. I've been using the fitbit since Mid November.
That being said, I am sure any pedometer would work if you just wanted to check out the amount of energy you are spending per day. There are also other manufactures who do not have wireless features.
I am not so concerned about the radiation since I also carry a cell phone and fly/travel often. (I am not sure, but I assume there is a lot more radiaiton from the cell phone and from flying.)
I am addicted to logging my data both caloric and from the fitbit. Check it out and let me know if you have any questions about the fitbit.