A team of MIT Scientists are working on an "in-body GPS" called ReMix to track the location of implantable devices. ReMix does not transmit a wireless signal but instead reflects signals transmitted by a wireless device outside of the body. This allows ReMix to have have an accuracy of plus or minus a few centimeters. The hope is to place the implantable device on shifting tumors and use them to track their slight movements or for use in specified drug delivery. Learn more about using GPS to track implantable medical devices at MIT.