The code itself is fairly simple,

String encodedHash = Uri.encode("#");
String phoneNumber = "*" + encodedHash + "105" + encodedHash;
startActivity(new Intent("android.intent.action.CALL",	Uri.parse("tel:" + phoneNumber)));

Sadly, Android doesn't have a native way of using the USSD response. If you're interested in seeing this in future versions, please star this feature request http://code.google.com/p/android/issues/detail?id=1285