It's been done since the 90's at least but there's been active interest and development in the last 8 years or so. http://wiki.bme.com/index.php?title=Magnetic_Implant

However "Implant work isn't ready for prime time. While Huffman loves his implant, he discourages others from getting it. "Most people don't understand the risks, and implant work isn't appropriate for most people." Those risks include infection and breach of the magnet's silicone sheath. The procedure itself is painful, and the results vary from person to person for unknown and unstudied reasons. Huffman doesn't see it as a candidate for study." http://www.wired.com/gadgets/mods/news/2006/06/71087