Got an assignment today to "research on technolgy [sic] and reaching youth with health messages." Might as well document it for myself and everyone else.
everything you need to know
Stanford professor Dr. BJ Fogg organized a conference (texting4health.org -- the name says it all) earlier this year addressing mobile-technology for health. He states, "Mobile phones will become the #1 platform for persuasion." Looks like the conference was done in partnership with, amongst others, the American Heart Association and ISIS.
This is excellent, it's not youth specific, but if you combine the info presented here with the pew internet research (where the above charts came from), i think it adds up to something that makes sense. and much, much more useful, telling data.
other stuff i found
not youth oriented, but this gives you an idea of different ways to interact with and present info to the youth via texting service.