You want SureSpot. End to end encryption, full deletion permissions, and open source. 
https://www.surespot.me/
It's free, but the author has a bitcoin address in the app for tipping!
https://www.surespot.me/
It's free, but the author has a bitcoin address in the app for tipping!
Let me get this straight. This app is designed to run only on fully compromised (back doored) devices right?
Lets move past that for a second and assume we don't care about those players who have that access, and are just trying to fend off script kiddies and low level advertisers / spamz0rs.
Now, where is my private key stored? How do I verify that I have the public key of your private key, in other words how do we know there is no MIM going on?
Is a key fingerprint easily available?
I use only jailbroken phones that I modify. It runs fine on my BLU phone. If you are concerned about what it does then I suggest you download the source and compile it for yourself.
When you want to invite someone it can be done in-app. You just need their username to directly connect to them. This app is not tied to a phone number or an email, or identity at all. Not that my phone is connect to me anyway.