Extract .xip file into a folder from command line?

Maybe try:

xip -x [path to .xip file]

That will unpack the archive into your current working directory.

As for extracting into a specific directory, there is not explicitly an option for this, but xip -x will extract into the current working directory. Therefore, cding to where you would like to extract the file should work; if you specifically need to automate this, a script to the effect of:

#!/bin/sh

xipfile="$(cd $(dirname "$1"); pwd -P)/$(basename "$1")" # a portable "realpath"

cd "$2"
xip -x "$xipfile"

Should do the trick I think?