Regarding the First Question:
Have you lost your mind? OF COURSE something harmful can come from this.
Sooner or later one of two things will happen:
1) Your phone sex friend will want more.
2) Your wife will find out.
And probably not in that precise order.
Now for the second Question:
If you have been "intimate" with this woman, is it safe to assume that the two of you have had sexual intercourse?
If so, then there has to be SOME physical attraction in order for that to occur.
But beyond all that, have you asked your friend how she feels about you and your relationship?