I'm thinking it would be similar to
tee, except with a popup window instead of a file. Here is an example of what I mean:
echo "hello world" | tee file
Puts the output in the file and in the console as input happens from the pipe.
echo "hello world" | something_here
Puts output in a newly created GUI and in the console as input happens from the pipe and then waits for the user to close the window.
Showing the output in real time would be preferable.