The link below gives a brief idea into the scenes of hacking implantable medical devices. As the blog states it has been termed - "Medjacking". The link has an overall picture and summary of several research papers that have found success in the realm of breaking into medical devices. My blog will delve further into details of the same and providing more detailed overall picture with additional technical details.

http://resources.infosecinstitute.com/hcking-implantable-medical-devices/

Let us start with the story of Barnaby Jack.
Profile: Ingenious programmer, hacker and computer security expert.
From: New Zealand
Place of Death: San Francisco 2014
Reason for Death: Accidental drug overdose of combining benadryl, heroin and cocaine. 
Conspiracy: Wondering why a prodigy would die to a puny overdose of hard drugs? Let's get to his background. Barnaby Jack was an avid hacker who successfully hacked into an ATM that automatically spit out bills giving the title "Jackpotting ATM". He showcased his awesome skills at the BlackHat Conference in 2010.
In 2011 he successfully hacked into insulin pumps causing it to pump out an overdose of insulin, high enough to kill the patient. He showcased this casein the McAfee conference. 
In 2012 he showcased his hack into a pacemaker at the BreakPoint conference. He showed how easy it was to assassinate an individual with that model of pacemaker. He famously termed "It was easier than in TV" - referring to the assassination of the vice president in the TV series Homeland. 
With such glory in the field of hacking openly showcasing his hacks of off the shelf medical devices and ATMs, the conspiracy theory erupted - he was assassinated by the government or medical device companies.