No, it's been a stock feature for about five years. If you have iMessages enabled and the contact you are corresponding with also has an iDevice with it enabled, the messages will use WiFi or data and go through Apple's servers. You can get delivered and read receipts on these. If the person you are texting has an Android, it will go through the carrier. Texts are green. iMessages are blue. There are several advantages to iMessages, one of which is that they will work in Airplane mode with WiFi on.