Helping my cousin through leukemia just wondering if there’s any app out there that actually helps with anxiety or panic attacks?

I’m an app developer, my cousin was recently diagnosed with leukemia and he’s struggling with anxiety and panic attacks

I help him however I can and now I’m considering building an app that could support patients like him to deal with anxiety or any other issues. Before I start I’d love to know has any app actually helped you or someone you know during treatment?