I have always enjoyed the feeling when the doctor's otoscope goes into my ear. It wasn't until very recently that similar feelings led to being turned on. In the doctor's office, the otoscope in my ear just felt good... not necessarily sexy.
The highly skilled LMT I see regularly, a lovely woman in her mid-40s, includes elements in her massages that I hadn't experienced before: and one of them is following her massage to my face and scalp with massage to both outer ears (helix, antihelix and concha.) This feels very warm and relaxing, in itself.
She then inserts her warm pinkies into my ear canals, and gently rotates her pinkies inside them. She takes her time with this subtle motion, and then leaves her motionless fingers inside my ears for a short time before moving on.
I was surprised at how good this feels. It's the only way that she "penetrates" me, but I think she knows I enjoy it.
It often happens that she and I will hear other male clients in one of the rooms next to ours (the rooms are divided by wooden walls but open at the top of each), as the guy asks the other lady for a hand job or "full service." (This establishment strictly does not provide such.) After one such incident, my LMT told me that she is grateful for clients like me whom she trusts, and who won't try to coax her beyond her regular practices. In my case, her practices include allowing brief genital nudity on my part (as she shifts my position); extended and deep massage of my bare hips; sweeping strokes to my inner thighs (but not to my scrotum, or to the cleft between my hips); and instead of a towel, her using just a thin sheet to cover me as she massages my lower abdomen and my pubic mound (but not my balls or my penis, the contours of which are clearly visible to her through the sheet.) She knows I enjoy all of these things, and the first few times my barely-covered penis left spots of pre-cum on the sheet, I apologized. She just smiled and said, "No problem. I trust you."
I think her slender fingers in my ears, and the pleasure she knows it gives me, are her way of saying, "This is a little 'extra' for you, and I'm glad it feels good."