The cheapest car navigation system costs several hundred yuan. If you have an old phone with a 3.5-inch screen or larger and GPS functionality, plus a car mount and cigarette lighter adapter, you can build a navigation system for just a few dozen yuan.
Install a mainstream free navigation app like Google Maps on your phone. Download offline maps in advance, and it will guide you accurately even without internet access.
Dashcams
For car owners, traffic accidents, disputes, and insurance scams are more frustrating than traffic jams. Dashcams truthfully record driving footage, protecting you from false accusations during incidents.While new dashcams often cost hundreds of dollars, repurposing an old phone costs just a few dollars—DIY saves you money.
Simply download dashcam software onto your old phone, mount it securely with a car holder, and connect it to the cigarette lighter for power. It offers robust features like loop recording and auto-start upon power-up, functioning nearly identically to dedicated dashcams.
Home Monitor
Cloud-based home monitoring systems keep an eye on your home, children, or pets to prevent accidents. However, these systems can be pricey. If you have an unused smartphone lying around, you can easily turn it into a remote monitor.
Simply download monitoring software onto the phone, connect it to another device via WiFi, and your old phone becomes a home surveillance camera.Stay connected to your home, no matter where you are!
Universal Remote
TVs, air conditioners, and set-top boxes all require remote controls. If you're tired of juggling multiple remotes and your old phone has infrared capabilities, you can transform it into a universal remote to control all your home appliances.
After downloading the app, first find the product model of the device you want to control (most common appliances are listed). Then use the "learning" function to teach your phone how to operate the appliance. If you're not at home, you can even control it remotely.
Document Scanner
Scanning paper documents into your computer for editing saves tons of typing time. But what if you don't have a scanner? Are you stuck?Actually, any camera-equipped phone solves this problem effortlessly.
Download scanning apps like DocScan to convert images into text. If you regularly handle large volumes of documents, transform your old phone into a personal office assistant!
Phone as DSLR
Capturing life's precious moments inevitably involves photography. While smartphone cameras have improved significantly, their performance still falls short compared to DSLRs.But lugging around a DSLR daily is cumbersome. Could your old phone become a DSLR?
Transforming your phone into a DSLR is surprisingly simple. Just attach an adapter and mount a DSLR lens—instantly creating a lightweight, portable version. It's three times lighter, yet delivers outstanding photo quality.
Anti-Theft Alarm System
While public safety is generally good in most areas today, petty thieves still exist. Installing an alarm system indoors or in your car adds an extra layer of protection. With a few modifications, an old phone can fulfill this function.
The DIY mobile anti-theft alarm system consists of an infrared detector, a phone number verification circuit, and a dialing circuit.First, store your phone number in the modified device. When intruders enter your home or your vehicle is tampered with, the system instantly dials the programmed number to alert you for immediate action.
File Storage Device
Can't bear to delete music, movies, or games, yet your phone storage keeps warning you it's full? That's where an old phone comes in handy.
Modern phones typically come with 8GB to 32GB of built-in storage. Not only can you save files like songs, movies, and games, but you can also use them instantly (watch TV, play games...)—far more practical than a portable hard drive. Of course, if you find the built-in memory insufficient, you can always add a memory expansion card.