What about something that conducts vibration + an exterior device?

I've tried taping a Zen Magnet to my finger, and while I'm sure it's nothing like having an implant, it was mildly amusing. For a few minutes.

I wonder if a piercing would be a suitable hybrid, giving additional sensitivity while still being removable. If detecting EM fields is the goal, I'm not sure there's much advantage to using a finger as the location.