I really don't see why there can't be a 'missing child/person" cable channel. Most cable networks have requirements in communities for so much public service. Providing a public service channel. It seems to me since all of this information is already digitized - it could just be put on a loop. Airports could be required to play it 3 hours a day, etc. I am not saying there has to be a whole story - 20 seconds with the child's picture and then another 20 seconds if the picture is available 'aged'.
If a child has just become missing (even if they don't comply with amber alert guidelines) they are still missing. Let's face it, even custodial issues can still place children in danger. The loop could be interrupted and flash traffic inserted for the specific area. This same loop (since it is digitized) could be available through the internet and thus available through a link on a library site, government site, etc.
It really doesn't have to be that hard. If you look at them Jaycee Dugard and Shawn Hornbeck didn't really look all that different. Perhaps if these offenders knew the pictures were out there and being broadcast it would make them think a bit more. I also heard a statistic recently that although many of the people in this country live below the poverty line they still afford cable television (above internet). You can get into a lot of homes through television. People watch sumo wrestling at 1 am they will turn to this channel occasionally and who knows what will happen.