About two years ago, I wrote a post asking what to do with old devices instead of throwing them away. My own proposals included giving them away, reselling them on eBay, recycling them for other purpose like servers or download clients, or scavenging some parts. Other people also comments what they did with theirs, for example setting up a Linux cluster with old TV boxes.
Another way to recycling an old (Android) smartphone – albeit you could always buy an inexpensive one – is to install and run Haven, an open source app that transforms your phone into some sort of smart security camera, but instead of only using the camera from the phone, the app also logs audio events using its microphone (array), as well as data reported by sensors.
One of you first reaction might be: “cool! somebody may an app that would allow hackers or government to make spying on your ever easier”. But actually, the app was initially intended to protect journalists against raids, or more exactly record their occurrence (as proof), and is released by the Guardian Project that aims to “create secure apps, and open-source software libraries that can be used around the world by any person looking to protect their communications and personal data from unjust intrusion, interception and monitoring”. Haven can also be used to monitor anything you care about, or even as a baby monitor for instance.
While audio and video is continuously monitored, the app only logs the data inside the phone if “thresholds” are exceeded (e.g. motion sensing, audio level…). If you decide to enable notifications, it does not transform your smartphone into another IoT device that relies on the cloud, but instead leverages Signal secure communication app, and the Tor network via Orbot app. A SIM card is not needed, unless you plan to use the optional (and less secure) SMS options.
The app only runs in Android, but iPhone users can still receive notifications via Signal + Tor, they’d just need to buy a cheap Android phone acting as the “camera”. You may want to check out the presentation slides for a quick overview, and visit the app page for more details.