Here’s a quick reference on how to have Keyring register a service defined in another plugin, since it’s not immediate from the documentation:

1. Define your service in a keyring-service-foobar.php file in your plugin directory as follows:

class Keyring_Service_FooBar extends Keyring_Service {

}

add_action(‘keyring_load_services’, array(‘Keyring_Service_FooBar’, ‘init’));

2. Add the following to your plugin file:

function register_foobar_service($keyring_services) {
array_push($keyring_services, __DIR__ . ‘/keyring-service-foobar.php’);
return $keyring_services;
}
add_filter(‘keyring_services’, ‘register_foobar_service’);

I hope that’s useful.