One option of Find My iPhone lets you remotely display a message on your device, such as contact info or a reward.
* Display a Message or Play a Sound If you've misplaced your iOS device, but you want to offer a reward or provide contact information, this is the option you're looking for. You'll be prompted to enter a short message, which will show up on the screen of your iOS device (just like a text message). You can also check a box to have the device make a sound for two minutes, even if the volume is all the way down, ideal for cases where you know your iPhone's somewhere in the living room, but you're just not sure where.
* Remote Lock: Realizing you've left your unprotected iPhone at a restaurant or doctor's office can be plenty stressful, especially when you think about all the personal information we put into our phones these days: pictures, contact information, e-mails, and so on. Fortunately, you can secure your misplaced device by sending a remote lock command. Just click Lock and enter a passcode. The device will be locked, even if it's currently in use. Any further attempt to use it will require the code be entered first.
* Remote Wipe: In the worst case scenario--the kind where you don't expect to get your device back--you can make sure that nobody else has access to your data by completely erasing it. Just click Wipe and check the checkbox that confirms you know what you're doing. It's important to remember this decision is irreversible: once you wipe your device, not only will it be returned to factory settings, but you won't be able to find it via the Find My iOS device service again. The good news is, if some good Samaritan does return your device, you can just plug it back into your computer to restore your data. But this should really be considered only as a last resort.
In each case, you'll get an e-mail message once the requested task has actually been completed. It may take a little while if the device is not available via the network, but the requested action should be completed once the device gets online.