Here's where the controversy begins. For many people, either RFID or GPS tracking of individuals constitutes a major privacy violation, even if intended for the good of the wearer.
Digital Angel frequently works with the government on projects to track criminals, particularly sex offenders, with their GPS technology. This has raised a lot of red flags with privacy activists, who argue that once criminals have served their prison sentence, the government has no right to continue surveillance, and questions the efficacy of such measures in the first place.
Their single most notorious product is an implanted RFID chip under the skin, which can contain a variety of critical information of the user, including medical allergies, social security number, current location, and others. This could be useful for any number of situations, from medical emergencies to even missing person cases. While at current there is absolutely no health risk, and full consent must be given in order to have these implanted, many privacy activists warn of a potentially slippery slope where people may one day be required to have such information that can be scanned from afar by third parties without their consent. As a result of this controversy, including multiple lawsuits—including subsequent lawsuits filed by stockholders in the company—Digital Angel has deemphasized its role in this product, and have instead focused on other products.
Slightly less alarming, but every bit as useful, is a similar packaged deal that doesn't go under the skin, but in a wristwatch, this one designed more for alerting emergency services when, say, a heart attack is happening or other medical problems. While many of the privacy concerns are still there, particularly with who would have access to this data and the amount of consent required to wear such a bracelet, they haven't quite caught on yet.
While the future of people tracking products are very much in question, many of their other products have received popular mainstream acceptance—and are quite profitable. Their innovations in GPS and RFID tracking technology will likely result in quite a few more products useful to society in the future, so keep a keen eye on this company!