How to obtain MAC address of WiFi network interface?

UPDATE:

Beginning Android 6.0, above API will give you constant MAC address for all the devices, which is 02:00:00:00:00:00. Refer below for details
http://developer.android.com/about/versions/marshmallow/android-6.0-changes.html
Found another post that claims to find MAC address in 6.0, not tested it though
How to get Wi-Fi Mac address in Android Marshmallow

There has to be a way to get this address since it's shown in the "Settings > About Phone > Status" of the phone.

Which means, if nothing else, you can go putter around the Android open source code, perhaps using Google Code Search, to figure out where it pulls that from.

Doing a bit of puttering myself, it would appear it is using getMacAddress() from WifiInfo.

Late answer, but it can help others with the same "problem".

The answer is really straight forward:

WifiManager wifiMan = (WifiManager) this.getSystemService(
                Context.WIFI_SERVICE);
WifiInfo wifiInf = wifiMan.getConnectionInfo();
String macAddr = wifiInf.getMacAddress();

The above code will get you the MAC address of your device, remember to have wifi enabled when grabbing the address. This code snippet should be used in your Activity.