The stealth messenger Briar is now in the public beta stage. Please consider to include it in F-droid (btw.: do you prefer a ticket in the fdroiddata issue tracker instead of putting this here?).
Here is the link to the sources: https://code.briarproject.org/akwizgran/briar/tree/master
Thanks in advance!
Briar now has an own repo because it uses binaries for Tor and therefore can't be included in F-Droid.org. It's planned to build them too, so it can get included.