I saw a much better written article on this (sorry I can't find the link) and assuming it was correct there are a few things left out here that were made clear.
It includes a battery supposed to last 16 years. Didn't specify the type, but nothing was said about the need to recharge it. Since all this does is distribute a microscopic dose of the drug each day, it should require a minuscule amount of power.
The dispensing is automatic, there isn't any way to tell it to dispense a dose, causing overdose or running out of the drug prematurely.
The one control you do have is being able to turn it on/off, so you can have kids without having to remove it. I hope the security is amazing and it requires something pressed right up against the skin to work. Stealing your SSN is one thing, but imagine if hackers could compromise home routers and have them run a program that flips the switch on birth control (makes the ones that are on go off, and vice versa) That would go down as the most catastrophic hack in the history of world for those affected.