The CNN article talks a bit more about privacy issues. This bit caught my eye:
It’s only available on iOS because Aaron says the app would have to collect information that could ultimately put users at risk to provide the same experience on Android.
I would like to see some details about this. Perhaps there's a way to work around that problem, even if it meant publishing on F-Droid instead of Google Play.
Once you need a normal server you might as well just have the server you already need serve the info preferably simply by grabbing a diff from previously so you reveal no info and without downloading a substantial portion of a chain. I swear people want to shove a blockchain into shit when it almost never adds any value whatsoever. You didn't address the fact about making an indelible link between you and your report and indeed prior reports if you are ever nabbed.