Hi Juan Manuel,
the WebServices needed to make it work are integrated in the master branch of Moodle (alpha version, not stable) so you'll have to wait until Moodle 3.0 to have a stable version with those WS. Alternatively, you can install the Moodle Mobile Additional Features plugin and you should be able to use it starting from Moodle 2.5.
Please let me know if you have any more doubts.
Regards,
Dani