I have made my own speakerphone myself.

I have 6110 Nokia.

I bought an Hand Free Kit.

I cutted the wire for the headspeaker.
Find the ground and the signal wire.
just put a Capacitor of (10NF, dont know exactly the seller gave me the capa) in serial with the signal line and connect an RCA jack and put it to the aux in of the empeg.

It works fine, but it is only mono sound.(right input for sound)
I plan to double the line with a jump for the 2 input of sound.It will make a kind of stereo sound.

I put it in my car dash so the mic of the hfkit is hidden, and when I have a call just switch to the aux source and you can still drive.

I'd like to install Perl for empeg but with no success at this time and dev a perl app with perl module for Gnokii : www.gnokii.org