OnMyWay, the free and simple notification application designed to assist users keep a person or group of people informed about your ETA to an event or location was released initially only to AT&T customers. Now the company behind OnMyWay, TeleNav has expanded the device and carrier compatibility list. The top four carriers have been covered.
As mentioned, the application is free to download just keep in mind data and SMS charges will apply when using the application. However, you'll likely save on SMS messages anyways cause your wife/husband/friends will no longer be messaging you and asking "Where are you?" or whatever other variation of hurry the hell up you can think of.