"smart select" tool in GIMP?

automatically selecting an object should be technically not very hard.

It selects objects by sharpness, color, contrast etc.

I have never seen a working tool in GIMP that can do that well. I have autoselected stuff by color always, and I know the "magic wand" tool (but have not used it much).

Is there a plugin, or can I tweak an existing tool so that it works like that?

I also need a tool to select a border and everything within that. Also didnt find a way to do that yet