As I like the ShoutBox idea by Simon Robins (https://challenges.openideo.com/challenge/urban-resilience/ideas/shoutbox/comments#comments-section), I also like your idea.
As the availability of smartphones seems to be kind of the key point in your idea, I wish you could find any (empirical) evidence for your statement: "This project is especially for urban slums, where more people have access to smartphones than life's necessities to survive." This evidence, of course, would boost your idea.
Your idea sounds great! What do you think about not converting the audio into text, but sending the recordings as audio data? We could keep a lot more emotions within the messages, what could make a difference when the community leaders listen to their people's concerns. We could also add a photo of the person who is recording the message, if this person would like to. Another barrier for community leaders to not take into account their people's consideration.
Another inspiration that goes a little further is to publish these messages on a website (anonymous or not), so anyone else can listen to and see these concerns. We could also integrate something similar to facebook's like button in the shout boxes and on the website, so other people in the community and in other (more or less) related communities could agree on the importance of the message. In the end, this puts of course a lot of pressure on community leaders, governments and maybe the whole world to tackle the biggest concerns of the poorest of people around the globe.
I know my last sentence sounds really big, but that is the thing in my head at the moment. And I believe that it is possible. Maybe this is kind of a thought for a new idea on the topic. I don't know. For the moment I am leaving it a comment.
I really like your idea of buddy programs and community groups. Buddies could meet and have fun together. Their families could be friends and this could develop to bigger community groups who could help each other when facing problems relating to climate change and other topics. In my opinion, it is also worth of thinking of increasing your initial idea by a mentor program. I personally really like getting advice and learning from mentors. Perhaps, we could motivate people in more established social positions and with better education, i.e. teacher, to show and explain community members the future consequences of climate change, so they can prepare and look for solutions earlier. In addition, mentors and community members could also develop idividual solutions together.
It would be great if you or anyone else on openIDEO could build on my thaugths.