Sorry for the self-promotion, but this sounds a lot like Peaked, an Android app I built.. It is privacy-first and your data stays on your device. Also it's completely free (as in beer): https://peaked.today
It serves my purpose (and that of some friends), so I have no plans to monetise or even update it.
I built this app for my own use - before that I was adding events to my calendar at the end of each day reflecting on that day.
Perhaps also interesting: I used ChatGPT and Codex to build this in one weekend. Almost everything came from GPT4 - from the app's name and logo to its branding, content, user flow and features (including source code, which is in Flutter). Pretty wild going from idea to release in just 2 days!
I released on Android first, iOS will be out in a few more days.
What about intercepting requests from other devices on the same network? Fiddler and Charles both let you set a proxy on Android/iOS devices pointing to your instance.
Would it be possible to extend this and run Charles Proxy on a server? I have used Charles to capture mobile traffic and always felt that having a machine running Charles on the same Wifi network as the mobile device was a hassle.
It serves my purpose (and that of some friends), so I have no plans to monetise or even update it.