These are the best things you can do with your old phones:
You can use them as a Security Camera
If its camera is in working condition then using it as a security camera for your home or office is one of the best thing to do with it.
Use it as a remote for smart devices
You can install smart devices apps on your old phone and use it as a universal remote.
Wireless mouse for your computer
Yes thats true, your old phone can be used as a wireless mouse! Just download an app like Gmote 2.0 or Remote Link for Android or Remote Mouse orMobile Mouse for iOS. These apps can be used as trackpads, keyboards and remotes.
Repair your car with an old Phone
There are many apps that can diagnose the error in your car. Some good garage apps to try are OBD Auto Doctor for iOS or Android, Car Diagnostics Pro and OBD Fusion. Many of these apps require an OBD Wi-Fi cable or Wireless OBD adapter to connect your phone to your car’s computer.