Sergio I haven't yet had a Kobo to try this on but my best information points to this plan:

.. Run XCSoar on a Kobo. Set it up to receive GPS data by TCP over a wifi link. I've tested this so I know XCSoar can do it.
.. Run an app called BlueNMEA on my Samsung Galaxy S2. This apparently lets you output GPS signal over wifi. I haven't tested this part.
.. Have a portable battery available in the cockpit to charge the S2 (or the Kobo) via usb if it runs out of power... though I'm expecting it to last at least 2 hours because the screen can stay off.