For anyone not familiar with it, the Roku Media Player was born the Netflix Player, a $99 appliance that you hook up to your TV, and your internet connection (it supports WiFi out of the box) and it allows you to play movies from Netflix's Watch Instantly catalog on your TV. Recently renamed to expand beyond just Netflix, they first added support for Amazon's Video-on-Demand, and just yesterday they announced support for MLB.tv. You have to have an existing MLB.tv account, and the same blackout restrictions apply so it's not going to replace cable any time soon, but if you're a baseball junkie, already have an MLB.tv subscription, and don't have a computer to hook up to your TV this could be a pretty good alternative. It can do HD quality, provided that you have a fast enough internet connection.
EDIT: Link to LA Times article.