Not specifically for general data tracking, but when I read this the first technology that sprang to mind was Ben Adida's (http://ben.adida.net/) Helios Voiting system (http://heliosvoting.org/):
"When you cast a vote with Helios, you get a smart tracker to track your vote all the way to the tally. No one knows how you voted, but you can track your vote and everyone can check the tally. "
"When you cast a vote with Helios, you get a smart tracker to track your vote all the way to the tally. No one knows how you voted, but you can track your vote and everyone can check the tally. "