Yes the hidden menu needs to be enabled in VCDS as follows.
1. Go to Navigation - 37
2. Click on Adaptation - 10
3. Type 50 into the channel box.
4. Change the value from 0 to 1
5. Click on test and press code
6. Exit out of VCDS.
7. Press <> and brightness to reboot the rns-510.
8. Then press setup for about 20 to 30 seconds to enable the secret menu (just keep your finger on it it will go from normal menu to radio then after about 10-15 secs to the hidden menu)
Basically you can vew info like map version software version etc. You can even see your digital speed (in KM/H) in one of the menu's but it's no different to what is displayed on the speedo
Carl