Excessive texting is clearly a problem. As reported in the New York Times, A study at Case Western Reserve University "suggests that the high school students who spend the most time texting or on social network sites (or both) are at risk for a host of worrisome behaviors, including smoking, depression, eating disorders, drug and alcohol abuse, and absenteeism."
Mental focus, calm, self-image, self-control, stress management? Hmm, maybe tai chi can help teens with this.