GNOME Keysign is a software for signing OpenPGP keys and to strengthen the Web Of Trust.
The application is written in Python and uses Gtk+3, GStreamer, and other GNOME technologies.
The project is hosted here: https://github.com/GNOME-Keysign/gnome-keysign
Note that the project is relatively young and things might change rapidly without notice. Also, functionality you'd expect is not necessarily implemented.
While the project aims to make it as easy as possible to OpenPGP keys, it also likes to test and play around with designs and to try new things.
See also: SafetyTeam