No app is going to tell you if you have S-OFF. You can only determine if you have a rooted ROM. Frenchy gave the best advice. Just go to hboot and see if you have S-OFF. There's a big difference between S-OFF and a rooted ROM, though. They are separate, and you can have one without the other. If you want to determine if you have root, just use the terminal emulator. If you must use an app, use something like wimax key checker. You want to use something designed to determine root, and do that only. If you use something more complicated, there could be other reasons why it might not realize you have root even when you do (titanium backup being a good example). Also, yeah, shootme has worked without root on and off for a while. Various OTA updates have either broken it or fixed it.