This has come up before on several boards . . In Kansas, if there is an autopsy, they're typically removed . . . if there is a cremation, they used to be removed as they were thought to damage the ovens but they are no longer removed in that case - they are simply consumed in the incineration. If there is no autopsy, and simply an embalming, they are left in place as long as they are intact. That information was supplied from the State of Kansas: Board of Mortuary Arts - (785) 296-3980.
Pacemakers are usually always taken out and destroyed or recycled after sterilization to developing countries where there law allows them to be reprogrammed and re-implanted. See
http://www.newsweek.com/2009/05/17/second-life.html
I have no idea how other jurisdictions view them (breast implants) postmortem, some States (this was a couple of years ago that the topic came up - so it may have changed since) required their removal as hazardous waste.
Kisses,
- Jackie