U.S. marketers using cell phones as an advertising outlet typically use text messaging to call cell phone users to action, writes Media Life (via MediaBuyerPlanner). "Right now the focus is on bringing people from an SMS text message into a mobile web environment," said Steven Siegel, director of sales and marketing at Enpocket, which provides technical and creative services aimed at mobile marketing.

Advertisers looking to tap into text messaging need to first register a five-digit code with all the mobile service carriers and then receive approval from each network. Mobile campaigns usually offer a promotion. "There has to be some type of interaction that provides value to the consumer," said Diana LaGattuta, director of marketing for Enpocket.

Traditional out of home venues tend to spark the initial invitation to participate, said Siegel. "The message is on a billboard or Jumbotron and the phone is a response mechanism, like a virtual click through."

"Advertisers are using mobile to make outdoor advertising interactive," LaGattuta says.