How to setup device as a bluetooth headset?

Question

Let us suppose we have a two devices with Android:

1. Custom android device with microphone, speaker, bluetooth and without GSM part.

2. Android smartphone (like a Nexus 5 or SGS4).

We need to make calls programmatically from first device through second via Bluetooth. What we are need to do to implementing it? Setup first device as headset? Or something else?

Answer 1

Step by step tutorial: http://developer.android.com/guide/topics/connectivity/bluetooth.html

One device as server, one device as client.