Laptops & PC: LocatemyLaptop
LocatemyLaptop (Windows 2000 and newer only) requires you to download and install a small software which installs in stealth mode - you'll never see it. To manage your registered laptop, you need to go to http://www.locatemylaptop.com from any computer and sign in to your account. Locatemylaptop is free for the most part - a free account lets you locate a single laptop on Google Maps. The only time you're really charged (US$ 3 per month) is when you need to use the service to remotely shred/wipe your data or get assistance from them to recover your property - but the paid plan can also be activated in the event that your laptop gets stolen - the small price you pay is well worth the added benefit. The paid (platinum) plan also lets you connect and track multiple computers from a single account.
MAC: Find My Mac
Find my Mac is an OS X Lion-specific service from Apple that uses iCloud. When you setup iCloud on your Mac, it automatically gives you the option to enable the Find my Mac service. Location services have to be enabled so that the location of the computer can be tracked accurately. In case of loss or theft, head to http://www.icloud.com, login with your Apple ID and it will display your computer's location on a map (it needs an internet connection). Select it, and you get the option to play a sound, send a notification message or remotely lock or wipe data from the drive. Keep in mind that once remote wipe is performed, your data is not recoverable and the computer cannot be located using iCloud again. You can also use the Find my iPhone app on iOS devices to locate, remotely lock or wipe your Mac.
iOS: Find My iPhone
Find My iPhone not only works with the iPhone, but also with the iPod Touch and the iPad. The free app requires you to have iCloud setup on your device with location services switched on. Head to http://www.icloud.com and sign-in with your Apple ID.
The page will show you the list of devices associated with your Apple ID and their location on a map. You can remotely lock them, wipe data, play a sound on the device and display notifications on it (the devices should be connected to the internet).
If you cannot access a browser, you can perform the same actions through the same app on any other iOS device.
Android: Avast Mobile Secuity
Avast offers possibly the most complete all-in-one security solution for Android devices and that too for free! It includes an antivirus scanner that scans local files and warns of malicious URLs, a built in app advisory (scans for apps with malicious intent), SMS & call filtering, SIM change notifications and a complete anti-theft and tracking service. A handy feature of the app is remote SMS commands - in case you can't find your device, you can trigger a siren, remotely lock or wipe data, display a notification or locate your device on a map - just by sendind an SMS to it with the correct keyword. The app hides so that it cannot be easily uninstalled.
Windows Phone: Find My Phone
On your Windows Phone, go to Settings, tap on Find my Phone and check the options that say 'Connect to these features faster' and 'Save my location every few hours'. Although this consumes a bit more battery. it allows for more precise tracking of your phone's location. When lost, head over to http://www.windowsphone.com and sign-in using your Windows Live ID. Go to My Phone > Find My Phone and from here you can map your phone's location, make it ring, lock it with a password, display a notification on it or erase the content remotely.
Blackberry: BlackBerry protect
Avaialble as a free download from BlackBerry App World, BlackBerry Protect not only keeps track of your phone's location, it also backs up settings and all your data to the cloud. If you lose or misplace your phone, go to http://in.blackberry.com/protect and log-in with your Black-Berry ID. Now from the browser, you can make the phone ring at full volume or see its location on a map. You can also lock the phone with a password or delete all the data. As an added bonus, BlackBerry Protect makes it easy to switch from one BlackBerry phone to another. Download and sign in to BlackBerry Protect on your new phone and it will automatically sync data associated with your ID to the new phone.
What started off as a Windows-only open-source experiment has now grown to support computers running Mac OS X and Linux plus mobile devices running Android or iOS. Depending on whether you want to use it on a laptop or smartphone/tablet, you can trigger specific actions either by sending an SMS or by sending a command over the internet. On a computer, you can remotely grab a screenshot, use the webcam to take a photo of the thief or hide your data. On a smartphone, you activate Prey by sending an SMS. Then you can remotely track, lock, sound an alarm or display notification messages.