tinyproxy does what you want.
We are really making it easy for all the companies that do the same that LG does.
Perhaps you would be happier with a script like https://gist.github.com/aarmot/5730468
There's also http://block.si/ cloud service but I haven't tried that.
Pretty sure there's a small dns blocker app for openwrt/pineapple as well, but don't remember the name of it right now.