There was a thread on here not long ago regarding using an old Nokia 3310 or sub-model thereof. I am personally following up on that using a Nokia 3595 that someone's chucked out in our office.
The Nokia F-bus protocol and wiring are documented. There is source code for a protocol implementation that I know works for a 6110.
I think I can wire a large capacitor, a 4V regulator and some resistors to fake out the battery sensor. I want my Arduino to control the power on the ME, so that will mean triggering the on/off switch and maybe finding a trace that I can use to measure whether the thing is powered up.