Would it be possible to design a device that would filter out television and radio commercials?

Apart from whether such devices would be ethical or legal, it seems to me that we have the technology available. Voice recognition and spam filters work fairly well, so it should be possible to combine the two.

The question arises as to what the device should do while it is removing commercials. If it is recording, it could simply not record For live viewing, it could replace the commercials with music. Alternatively, it could delay showing the broadcast by a few minutes, making it possible to screen out the commercials without any breaks.