1) 3G Flyer
2) S-Off (get yours from Alpharev soon!)
Using root explorer or your favorite text editor edit the build.prop file under /system/build.prop and edit the following lines:
ro.ril.reject.cs.ss.enabled=0 ro.ril.reject.mo.ussd.enabled=0 ro.phone.function=1
ro.bt.profiles = 4270403 service.brcm.bt.ag_supported = 1
Save your changes and reboot your device. Look under the programs menu you will see the phone app you will now be able to make and receive calls.
Tested on a 3G UK unlocked flyer using an AT&T SIM.
EDIT: now with full BT support!!