A new study looks at how the frequency, nature, and content of parent-adolescent cell phone calls relate to the quality of the parent-child relationship in terms of self-esteem, perceptions of family conflict, and family dynamics, including closeness and support:
http://psychcentral.com/news/2011/06/28/cell-phone-can-improve-connection-with-children/27298.html
http://well.blogs.nytimes.com/2011/07/01/what-cellphone-calls-say-about-parent-teenager-relations/