An emergency GF communication capsule is a transmission pod mentioned in Metroid Prime 3: Corruption. One was sent by Gandrayda to the Galactic Federation while she was searching for the Pirate Homeworld. It was found by a "reconnaissance unit", and it revealed the existence of the Pirate Seed, leading to the Federation's decision to destroy the Leviathan and assault the homeworld. The capsule was Gandrayda's last message before her corruption.
Later, when Samus arrives on the homeworld, Aurora Unit 242 contacts her and says that the message revealed that the Seed is protected by a cargo supply route, the Skyway, and that the Command Courtyard appeared to be its main entrance, although Samus needed to find protection from the Acid Rain. This ultimately led her to discover the Hazard Shield and actually encounter Gandrayda.
It is unknown what the message actually said.