The app has many of the features of Find My iPhone, but it has additional features that you might find compelling.
For example, if your phone is running out of battery, it will take note of its location. You can sign in from any browser and see the phone's last-known location. If the phone is lost, you can also send a loud alarm (and it is loud) to locate your phone if you think it is nearby -- even without a SIM card. The alarm starts at a low level, and then continues to ramp up to maximum volume. Another feature is contact backup, which backs up your contacts every day.
Signal Flare gives you quite a bit of remote management of your phone. It goes a bit further than Find My iPhone and I find the last location notification with a weak battery a particularly good idea. Some users have reported crashes, but that can be fixed by giving Signal Flare access to your contacts via the settings.
Signal Flare has been optimized for iPhone 5, and works on any iOS device. It requires iOS 4.3 or later.