Apparently, magnets in multiple fingertips allows you to sense magnetic fields, specifically their dimensions and strength in the particular part of the field your hand is in, in three dimensions. You can sense electricity by tingling, she says, so you don't have to worry about hard drives and stuff because you wouldn't accidentally touch them when they were running due to the tingles, and the magnets would not be strong enough to affect anything on the hard drive when it was off.
I might get something like this done in one finger on each hand, except it is unlikely I would be able to tolerate the circumstances of any operation other than fully professional surgery. Also, I am pretty sure that the nerves in your fingers would attempt to adapt to this new sensation and dull themselves over time. Thus, you would always be able to feel the tingling, but your regular sense of touch might dissipate, the same way sensitive piercings (nipples, egs) lose feeling after awhile.