Although I believe those things utilize RF (radio frequencies) for communication, any electrical device will emit some levels of electromagnetic waves. However, the level of these emissions is so small, even a cell phone puts out way more. Think about the range of a cellphone compared to the range of one of these transponders. Additionally, you get far more exposure to cosmic and UV radiation from nature on a daily basis. Your exposure to and absorption of C-14 and gamma radiation on a day to day basis is also at a higher level. Unless you are hypersensitive to such things, you needn't worry. If you are, natural things around you would have given you a far higher dose by now, in which case, you might want to be wearing lead shorts.