Samsung makes one, as do a few others. They are not cheap. You're looking for a "terestrial HDTV tuner". It's also available included into both DirecTV and Dish system HDTV receivers. You only need to add a separate off-air antenna to the satelite system to receive the off-air digital channels.

The cost of a stand-alone HDTV receiver is almost the same as for a satellite HDTV system. Of course, you would have to subscribe to satellite service to get the receiver activated.