Read specific variable from phone configuration

[saivo]

I want to create simple web form for users to allow set or unset call forwarding.
It's easy to set some values using push xml file to phone.

But problem is - how to retrieve some variables from phone configuration.
I want to know - is currently call forwarding active or not.
Also - if active, then - to what phone number it is set.

Can't find in documentation anything about it - just - ho to push configuration, but not pull.