http://www.nfl.com/news/story/0ap100...adium-near-you

Excerpt: "Even if it's "not official," the yellow first-down line was a master stroke in the advancement of NFL television broadcasts.

The imaginary line gave fans at home a clear view of how far offenses needed to go to move the chains. Could fans in NFL stadiums eventually receive the same helpful tool?

It's not imminent, but it is possible. Alan Amron, with the financial backing of former player and sportscaster Pat Summerall, has developed the First Down Laser System. Amron said the system projects a first-down line across the field that can be seen in the stadium and on TV.
Amron met with the NFL in 2003 and again in 2009 to discuss to possibility of implementing the technology." Read more...