Not exactly all-in-one, but this could help
http://www.hauppauge.com/pages/produ..._mediamvp.html

Finding a 15" monitor should be easy, just needs to have S-video or normal Yellow-White-Red connections.

There are several other products, 'Digital Media Players', that hook up to computers and can display them on a TV. There are some wireless ones as well, though they are typically of lower quality.