In most cases, it will just end lying in some corner of your house. And soon you will forget it. But it doesn't have to be this way.
Here are some clever uses of your old Android phone or tablet.
#1 Use it as a security camera
You can use quickly convert your old Android into a surveillance camera. Download IP webcam or Android from Google Play. Once you start this app, it will show you an IP address, enter it in your browser, and that's it. Now your stream live video feeds captured by your Android's camera. If you have a toddler in your house, then you can use this setup as, nanny cam. See gif Related: How to Use Your Android as Surveillance Camera#2 Track with GPS
Let say you are visiting an unfriendly neighborhood, where your car (or any item) might be stolen. Just put your old smartphone to silent mode, turn ON GPS and hide it. Now you can track it, without anyone know it. You can go one step further by installing anti-theft apps like LockWatch or Cerberus. Other than tracking GPS location, these apps can also capture images, record audio from remote computers.#3 Universal Remote control
Use your spare Android as a permanent remote control for your chrome cast or smart Tv.
With remote control apps like the remote mouse, you can pause and play videos on your computer. Some DSLR has Android app, to control them remotely. Same thing with Philips hue lights.