During the war, a soldier was tortured by the enemy because had had a government issued cell phone.
He returns to the USA, severely disfigured and breaks out of a hospital, disappearing. He starts a cult of "Anti-Technology" followers who are marked by bar-code tattoos (these cult members seem to be everywhere, teachers, law enforcement and so on.)
The disfigured veteran sent a chain letter to a nerdy teen, the teen forwards to 4 friends and his sister. The chain letter states that if you don't pass on the letter in 24 hours or less you will die. The teens who get the chain letter ignore and delete it, as soon as it is deleted the disfigured veteran shows up (using technology to track them down) and kills them with...A CHAIN!
In the end, he kills everyone who didn't forward the letter, including a cop who insisted that the letter be forwarded to him for evidence.