Android 5.1 Lollipop was not a huge monumental update to the Android software, that doesn't mean that it didn't introduce some important and otherwise huge features. At least one new feature not only seems to be setting Google and the Android OS up for being in line with the killswitch law for future devices that need to be in compliance, but it also helps to secure the device of anyone who has the Device Protection feature enabled just a little better than what things were without it, which is pretty big for anyone who can enable the feature on their smartphone or tablet.
While the software update details from Google's official announcement a few days ago state that Android 5.1 brings Device Protection to the table, it's important to understand that this doesn't mean every single device that gets updated to Android 5.1 Lollipop will have Device Protection. It seems a bit confusing, and that's why we want to help clarify things as much as we can. All future devices that come running Android 5.1 Lollipop out of the box will have this enabled, or the capability to have it enabled, and as of now the Nexus 6 and the Nexus 9 will support it if Android 5.1 is running on the device. As for all previous Nexus devices, which includes the Nexus 5, Nexus 4, both generations of the Nexus 7 tablet and the Nexus 10, Device Protection is not included even after the update to Android 5.1 Lollipop.
Activating Device Protection doesn't really have to be initiated, but you do have to have at least one Google account already on the device with a secured lock screen enabled using a password, PIN, or pattern, and of course your phone or tablet has to be compatible. If you're unsure about device compatibility but you are running on Android 5.1, you can figure things out by enabling a PIN , pattern, or password for your screen lock and then disabling it, which should alert you that Device Protection will no longer work, if it was on in the first place. If you're curious about whether or not Device Protection is something you'd even want, just weigh out having extra security vs having less security. Extra is always better. Essentially Device Protection just adds an extra layer of security to your device. It's the same idea as two-factor authentication adding an extra layer of security to your Google account, although they don't work in the same way, nor do they really do the same thing when you get down to the specifics.
The way it works is that if your device is lost or stolen, the device can be protected in a number of different ways. It's also worth noting as we have mentioned before that Device Protection persists through factory resets, so if your device is stolen and it's wiped through a factory reset by the thief, they will still not be able to get into the device as they will be prompted to sign in with the last remaining Google account that was on the device before it was wiped. Device Protection also keeps thieves from removing the last Google account if there was more than one, or if there was only one account to begin with, thus keeping Device Protection intact should your lockscreen not be enough to stop the device thief from getting to your personal data. In the event that someone gets a hold of your Google account password prior to or during the theft of your device and changes it, you will have a 72-hour window to change the password back to something you have personally set. During this 72-hour timeframe, the device cannot be logged into with that Google account in the event of a wipe, so for a period of three days, Device Protection will continue to serve its purpose and give you a chance to reset things, after that, all bets are off. Google also mentions that Device Protection may or may not work as they intended if you have unlocked your bootloader, so if your device is rooted, or rooted and running a custom ROM, Device Protection functionality is not guaranteed to work correctly.