Recently a team of sea turtle biologists set out to capture and tag sea turtles in Chassahowitzka Bay, Florida. Once turtles are captured, biologists collect measurements and look at their overall health. Then a satellite tag is attached to the turtle so scientists can track its movement. Where a turtle travels provides valuable information necessary for the animal’s protection.
Measuring a loggerhead
A satellite tag secured to the back of the sea turtle
These tags don't pose any danger. Sometimes you can get biofouling (barnacles, algae, etc.) growing on it, but that happens on the shell as well anyway. The tags eventually fall off, either from failure of the epoxy, or eventually the turtle shedding the scute as it grows. However, it can stay on for as much as a couple of years.