Globes reports on the first steps towards rendering mechanical pacemakers obsolete: "[Israeli researchers] created heart cells out of human fetal stem cells, which he implanted in a pig's heart. The pig previously underwent treatment to artificially slow its heart rate. The implanted tissues partially corrected the resulting defective heart rate by in effect constituting a biological pacemaker." More than half a million people use pacemakers in the US alone. The devices, like most implants, are comparatively short lived and expensive. Replacements based on regenerative medicine and stem cell engineering would be a very big deal - but there is a lot of work to be done to get there.
Link: http://www.globes.co.il/serveen/globes/docview.asp?did=840163&fid=942