Ooh, I know... an AppleScript Droplet. Just fix the shell path in this script, and save it as an application in AS. I think that this should work. Or at least it will give you enough to run on.
Code:
on run
display dialog ("Drag'n'drop text files to un-line-wrap them.")
end run
on open (txts)
repeat with the_file in txts
do shell script "/path/to/your/script '" & POSIX path of the_file & "'"
end repeat
end open
You can also just type in the entire script into the AS file if you don't want to have it in a separate file. Just be careful with quoting and escaping things.