I took one of the phones home to reverse engineer the LCD. After about 10 minutes with the logic analyser, it was clear that it’s based on the Hitachi HD44780 or compatible controller.
Just connect the contrast pin to GND, then contrast is perfect for most projects – unfortunately the LCD is meant to be viewed from an angle, and is not good for a front panel etc. that you will view front-on.
I drew up the connections here:
Some pctures of the LCD and the adaptor i soldered up.
The phones contain some other nice parts, a DC-DC converter module some Xtal’s, Electret microphone, speaker etc.