1. Make Your Phone into a Listening Device

If you want to turn your phone into a spying device or a baby monitor, then you’re in luck. After enabling the Auto-Answer function, muting the microphone, speaker, ringtone, and vibration, simply put your cell phone in your chosen location, then remove yourself to another place and call the handset (using another device or phone). It will answer automatically without making any sound! And you'll be able to hear everything. Pretty cool, huh?
2. Take Photos Underwater
Smartphones are already waterproofed, but if it happens that yours isn’t, there is something wonderful you can do to make it so. Have a look at the above video to see how it can be done

3. Make Sure No One Can Use Your Stolen Phone
Every phone in the world has its own 15 digit IMEI number, which you can find by opening your dialer and typing *#06# with the keypad. It's also visible in Settings > About > Device > Status. If you’ve irretrievably lost or had your phone stolen, you can contact your phone company to block your device, simply by quoting your unique number. If everyone did this, phone theft would have virtually no purpose.

4. Turn Your Phone into a Microscope
Using a lens that you can find on a normal laser pointer you can manipulate your phone to magnify up to one hundred times the normal size. This will be great for showing kids cell nuclei, for instance. What’s more, the images you record will be digital, which could never be said of the microscopes we grew up with!

5. Make Astonishing Holograms!
Holograms are so incredible that most of us still have a hard time believing they are even possible. But the amazing truth is that you can make them yourself, using your own cell phone. Just wow! Watch the illuminating video above.

6. Set Up the ‘Face Unlock’ Feature:
People use different security measures to prevent others from using their phone. The most popular choices are a PIN, password, pattern gesture, or a very insecure finger swipe. Yet your phone can also do something incredible, which will certainly stop anyone using it. Android has a Face Unlock feature, that means only someone who looks identical to you can log into the phone. Simply go to Settings, Security, then tap Screen Lock and proceed to Face Unlock.