Starting from version 1.8.14 (beta 1.0.134) you can use Bluetooth earphones and headphones with Mtalk for Android.
Using a Bluetooth device with Mtalk is very simple and similar to the usage with the built-in cellular phone app : just connect the device to your Android smartphone/tablet and the audio will be automatically redirected to the Bluetooth device also when calling with Mtalk.
During a call you can redirect audio from the Bluetooth device to the regular speaker and back clicking on the Bluetooth button located on bottom of the call view.
You can do the same simply connecting or disconnecting your Bluetooth device as you would normally do with the cellular phone app.
Some Android devices may need to enable the option Options / Advanced Settings / Bluetooth / Re-init audio streaming to ensure proper management of the audio speaker changes while in call.