http://www.theregister.co.uk/2011/10/27/fatal_insulin_pump_attack/page2.html
The same security consultant who talked at blackhat showed a tool at a security conference that will allow you to scan for Medtronic devices in your area, recover the serial number of the devices and then connect to them. With the antenna that he built he has a 300 ft range as well.
The big kicker here is that a vulnerability was found that allows you to recover those serial numbers. Before that was the only layer of security you had that kept people from accessing your pump.
Makes me glad that Medtronic has finally decided to make security a concern.