American Idol prominent display of its sponsors' logo and products had been noted since the early seasons. By season six, Idol showed 4,349 product placements according to Nielsen Media Research. The branded entertainment integration proved beneficial to its advertisers – promotion of AT&T text-messaging as a means to vote successfully introduced the technology into the wider culture, and Coca-Cola has seen its equity increased during the show.
What service did AT&T promote on American Idol as a way of voting? 
text-messaging