Everything can be hacked -- that's an important detail to keep in mind as we start cramming wireless radios into our bodies attached to medical implants. Researchers have been working on ways to protect devices like pacemakers from ne'er-do-wells looking to cause, not just e-harm, but physical injury or even death. A new system developed jointly by MIT and UMass is much more sophisticated that earlier solutions, can be used with existing implants, and is worn outside the body allowing it to be removed in the event of an emergency. The shield, as it's called, acts as a sort of medical firewall, protecting implants from unauthorized access -- doctors send encrypted instructions to it which are decoded and relayed to device, while it blocks any signals not using the secret key. All that's left to do is figure out what sort of person would mess with someone's defibrillator.