This was something my wife and I also wanted. I downloaded the free MS OneNote app, created a new OneNote notebook on the free MS Live service, shared that with my wife, created a single OneNote page with checkboxes, pinned the page to the front screen and voila! A free list manager that synchronises across everywhere I can run OneNote (and that's available on just about every platform)! Took about 10 minutes to create.
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