Maybe using something like NFC? so you come near to a poster and it pushes a URL or something to you? Or a 'smart billboard' perhaps: http://mashable.com/2011/

Maybe using something like NFC? so you come near to a poster and it pushes a URL or something to you? Or a 'smart billboard' perhaps: http://mashable.com/2011/04/16/smart-billboard/ http://mashable.com/2011/04/16/smart-billboard/