Android, Device unique key

** required : cellular model chip

TelephonyManager tManager = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
String uuid = tManager.getDeviceId();

** required : WiFi on

WifiManager manager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
WifiInfo info = manager.getConnectionInfo();
String address = info.getMacAddress();

** required : Android 4.0 (API 14)

String uuid = Build.SERIAL;