Speaking of features from smart phones - pop-up keycap menu?

[Skip Montanaro]

The question about iPhone treatment of spc-spc reminded me of a
feature of my Android phone which I would find handy, at least when
typing text. While composing email or SMS on my phone, if I touch and
hold a letter, after I short pause (0.25-0.5 sec?) a menu pops up
showing me alternative characters (glyphs?) reachable from that
keycap. Just drag to the character you want to insert at that point. I
use SWYPE on my phone, but I suspect this behavior is similar to the
native keyboard as well.

I think it would be great to have something like this for traditional
keyboard input. I haven't any idea what the proper UI behavior would
be (as I don't have a "soft" keyboard). I use the X11 version of GNU
Emacs, so there is probably more flexibility in that interface than
when run via -nw. I have to believe some resourceful person in the
Emacs community has already implemented something like this.

Skip