This isn't radio, but it's very appropriate to our context. In South Africa we are partnering with our National AIDS Helpline to provide HIV counselling via MXit, a very popular mobile text-chat application used by millions of South Africans, especially youth.
We've noticed that sexual health questions come up a lot (should I have sex, genital warts, etc) and that youth are remarkably comfortable chatting with counsellors via text on their mobiles. It's completely anonymous, and youth can chat anywhere and no one need know. So you can be in a rural area, an informal township, on public transportation, but you can text-chat.
It's also very cheap for the user (a counselling conversation will cost them less than US$0.05).
To read more, see
http://mobileactive.org/case-studies/red-chat 
Use of mobile instant-message chat
We're not using SMS here. Proving counselling using SMS would be hard because:
- It's expensive
- Each SMS is only 160 characters
- It would be hard to maintain a conversation thread
- It would be hard for counsellors to counsel multiple people at the same time.
Clients access this service MXit, an application that millions of South Africans have downloaded to their phones. It allows people to send each other messages with a data connection, which is way cheaper than SMS. (MXit is like BBM, the Blackberry chat application, or like gtalk on a computer.)
Anyone interested should go to http://www.jamiix.com to see the tech that is being used for counselling provision.
The counsellors are trained HIV counsellors. They had to get a couple of days' training to do chat-counselling. They found it really easy and many prefer doing counselling on chat as they deal with a lot less hoaxes (on the telephone you are stuck with the hoaxer until protocol has been followed; on chat you can just ignore the hoaxer and counsel others until the hoaxer comes around, or goes away).
youth-mobile phone app