If you have an old Android phone you've upgraded from lying around, there are tons of projects to put it to good use, but this one is relatively easy and can bring you a little peace of mind: Turn it into a Wi-Fi web or home security camera.
Instructables user depotdevoid took his old Droid Razr Maxx and decided to turn it into an always-on, internet-connected webcam he could monitor at any time. If you want to do the same, you'll need a few things to make this project work. A copy of IP Webcam (Free, $4 Pro) from Google Play, and a soldering iron (if you don't want to just use USB power—depotdevoid's Maxx has a broken USB charging port) to add external power, and a mount for your phone are all it really takes. He uses his to watch his 3D printer when he's not in his garage workshop, but you can use it to keep an eye on package deliveries, watch your pets during the day, or just see the view from your home window.
Once the app is installed and on your home network, you have to make it internet-accessible so you can view it when you're away from home. He explains how to do this in the post, but we're sure most of you are familiar with the concept of port forwarding. If you're looking for easy ways to assign a dynamic hostname to your home network, we have some great free options for you there, too. Hit the link below for the full tutorial, from start-to-finish.