Hmmm I do not really see anything in jQuery events that will easily give you an x y coord for the caret.
However there are quite a few ways for detecting the caret position in a text field:
http://laboratorium.0xab.cd/jquery/fieldselection/0.1.0/test.html
Is it possible to programmatically detect the caret position within a <input type=text> element?
Caret position in textarea, in characters from the start
Using this, you could try to estimate the pixel coordinates for the tool tip.
If you want it to be more exact use a monospaced font inside of your text fields.
//depending on size of font
var charWidth = 10;
//using any number of the above methods to get caret position
var caretPosition = getCaretPos('#myTextField');
var textFieldOffsetX = $('#myTextField').offset.left;
var toopTipPositionX = caretPosition * charWidth + textFieldOffsetX;
It is not exact and it is not going to be perfect, but it might be close enough.