“In theory, TVs and PCs were supposed to converge and spawn one hybrid media device. In practice, they touch on the couch without breeding. TiVo buffs up your TV with PC-style software that ends the pain of VCR programming. YouTube delivers a searchable trove of instant-play clips to your computer screen. But when you plunk down on the couch to relax, you probably don’t want to search YouTube with a remote wand.”