Sorry, I cannot help directly. I looks like neovento uses the FSO stack, so there is probably some dbus command to find out the signal strength.
As it is debian based you could install 'cu' using 'apt-get install cu'. You would probably need to kill the FSO daemon that is accessing /dev/ttySAC0 before 'cu' will be able to access it.
I suggest you look for information about dbus access to the FSO stack.
