The Future of the 30-Second Spot
TiVo and video-on-demand allow television viewers to skip commercials, but some of same technology will soon be used to permit creation of commercials that behave more like smarter version of direct mail: customized not just by neighborhood, but ultimately by household and perhaps even by viewing habits; host of companies, including Invidi Technologies, Visible World, Navic Networks and OpenTV, are selling their technology and services to cable operators and satellite providers whose set-top boxes afford them direct access to viewers; ultimate goal is to make ads more relevant to lives of viewers, who might be even eager to watch them; photos (L)