L-Phone?

It's actually pretty easy, when a ring comes in, you just need to:

sip show peers
to see if the call is coming in via SIP/IAX protocol, if it does, then you just need to accept the call by:
phone_control accept -p SIP --node <node number you got in the previous step> --encoding <either Raw or uLaw> --idevice <the sound input, usually /dev/microphone, but could also be your Bluetooth headset, so /dev/usb/1/device> --odevice <the sound output, usually /dev/sound, or /dev/usb/2/device for Bluetooth> --controlchar <the escape sequence that will automatically be sent to the OS by the Icon you press in the GUI, usually ESC-IfH for the "Done" Button>

If the call isn't coming in from SIP, then it's a real GSM call, and that uses another interface, so do :
zaptel show incoming
to see which zaptel channel is being opened, and call phone_control again, but replace -p SIP with -p Other, and give it the zaptel device via the --device /dev/zaptel? (where ? is the number of the zaptel device you got from the previous command). Remember that zaptel only supports uLaw encoding, and you won't be about to send it to your Bluetooth, because there is a bug in the phones current firmware version (the kernel as it were) which screws up the timing.

I can't wait for the next firmware because it will support dymanic module loading, so you will be able to compile the Openswan modules and do true IPSEC VPNs directly to another phone that has the same setup as you. It's gonna be a bit slow, but very secure.