GPG on the Mac has been quite an issue always. Several choices to install and hard to configure. Now seems that GPG native tools for OS X are back to life at the GPGTools project, providing a single easy to use installer.

GPGTools is an open source initiative to bring OpenPGP to Apple OS X in the form of a single installer package

So I installed the package, logged out and in again for the PATHs to take effect, and got the agent up and running by executing

gpg-agent --daemon

(It will be automatically started when you restart)

Now, to configure Maven to use this GPG2 version and the GPG agent I added a profile to my ~/.m2/settings.xml

    <profile>
      <id>gpg</id>
      <activation>
        <activeByDefault>true</activeByDefault>
      </activation>
      <properties>
        <gpg.useagent>true</gpg.useagent>
        <gpg.executable>gpg2</gpg.executable>
      </properties>
    </profile>

This way the agent only prompts for the GPG key password once for each session, and Maven uses the right gpg executable.