According to Capcom's official blog on January 24, this Apollo Justice keychain will be available from GameStop as a preorder gift, and from Capcom's online store as a gift with both preorders and post-release orders of Apollo Justice: Ace Attorney. People who have already placed their preorders will receive the keychain.
Notes: This is an offer in the US.
Not as good as the Phoenyx Wright plushie given out by GameStop some time ago. :'(