As a diabetic ...
The reason for connectivity is to improve management of the disease. The reason for wireless is for the patient's comfort and convenience.
Using a handheld device (not implanted), I take anywhere from 6 to 12 measurements of my blood's glucose level, each day. These implanted devices take measurements anywhere from once every 3 seconds to once every 3 minutes, or so.
That's a LOT of data points.
Using that data to chart a patient's glucose levels greatly improves the ability of both doctor and patient to visualize the progression of the disease and its treatment.
Manually entering into spreadsheets the thousands of data points produced by implanted devices between consultations and then producing graphs from that data is prohibitively labor-intensive. We're talking about many, many hours, even days, of going through points, one by one, and manually typing the figures on a keyboard.
Connectivity allows the use of vendor-supplied software to (a) gather the data points and then (b) create visualizations from that data. The handheld device I use includes infrared connectivity. Many others use Bluetooth (most popular) or some other protocol.
Attaching a cable to one of these implanted devices is extremely uncomfortable, akin to sticking a syringe into your belly/back and then having someone pull it to the side for 5-10 minutes while the device and the computer handshake and get down to work. You don't want to do that.
I do agree that security has been pretty much overlooked in these devices.
And to those of you who wonder what could go wrong ... what the risk is ... well, I guess you don't know any kids, or any assholes. Some people just like to hurt other people. They don't need a reason ... just the fact that it can be done, and that someone will absolutely be hurt by it, is enough.