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Most of us have at least one old Android phone sitting in a drawer. Maybe it was replaced by an annual upgrade, maybe the battery stopped lasting a full day, or maybe it simply lost the race to the latest flagship. Whatever the reason, it probably still has Wi-Fi, a screen, a speaker, a battery, a camera, and a pile of sensors Home Assistant can use. If you have an old phone or two, why not turn them into sensors and dashboard displays?
Just because the old phones aren’t being used as mobile devices, it doesn’t mean they’re not worth considering for other uses. Sure, the camera may be dated, cellular reception stuck to 3G, and the CPU lacking in all departments compared to newer handsets. But these older phones can be invaluable additions to a Home Assistant setup, largely because they don’t need to run games, last all day in your pocket, or take the best photos on vacation. It just needs to be set up somewhere and connected to Wi-Fi.
Inside each Android device is an array of sensors and parts, many of which can be integrated within Home Assistant. The best part is you don’t need to spend hours setting everything up. All that’s required is the Home Assistant companion app. It’s not just a means to conveniently interact with your smart home while away from the PC, but it’s also great for adding sensors and data inputs for a variety of stats. So long as your old Android device can run the app, it can help power your smart home.
I decided to try some things out. Armed with nothing but an old Android phone, I set it up inside and checked what was available for the software to read from the hardware. This included battery charge state, Wi-Fi signal strength, light level, pressure, and more, all supported by the device. This is actually really handy, as I could set light detection to automatically turn on lights as the sun sets, send off alerts if something abnormal is detected, and even wall-mount the phone to create a mini Home Assistant smart home panel.
And it’s all thanks to the cool sensors included in modern smartphones
With a dashboard installed at various locations, for instance, our garage, we can interact with the smart home without needing to fetch our phones. All that’s required is a quick unlock pin, and then the various elements and controls are all available. The garage device is particularly useful thanks to it being where our gym is, the cars will be parked, and the home lab resides. Should the temperature get too high within the garage, alerts are fired out, and the smart lights can be interacted with like a standard switch.
Most phones have a working proximity sensor too, which can detect when someone comes close to the phone. For our wall-mounted dashboard, this is invaluable as it can wake up the screen without needing to tap anywhere. Then there’s the built-in speaker, which Home Assistant can use to relay information. This can be in the form of an alert that a door has been left open or a laundry cycle has completed. A smartphone is a two-way street, offering a means to input and output.
Your drawer with old Android devices is a Home Assistant goldmine, not e-waste
Why spend money on a dedicated smart speaker when an old phone could very well do everything your old Echo can (and so much more)? I don’t miss our old Amazon smart speaker one bit after giving it the boot. Phones weren’t designed to run 24/7 and be wall-mounted for use with Home Assistant, which is the unfortunate truth compared to dedicated hardware that was designed for this very scenario.
You can reduce some of that strain by using a smart plug to keep the battery within a sensible charge range, monitoring battery temperature where supported, and avoiding permanent installs with swollen or damaged batteries. Battery removal is possible on some devices, but it is a project in its own right, not casual advice.
I replaced everything with local-only hardware, but this was the most difficult.
Smart home devices aren’t cheap. You can absolutely buy new hardware at a fraction of the price of what they used to command, but even then it’s pricey to completely kit out the humble abode. That’s where reusing old products can really make a difference, particularly using old Android-powered tablets and phones. Most of them will be just fine for use as a dashboard, though specialized smart home devices will also be better for specific tasks.
I love using my Sonoff leak sensor in the utility room and humidity sensor in the living room. These won’t be replaced by an old Android phone. But what these old devices can do is have some new life breathed into them as a dashboard or sensor that can be integrated into a wider smart home setup. Just because your old smartphone stopped being useful as a daily driver, it doesn’t mean you should keep it locked away indefinitely.
While I highly recommend reusing any old devices you may have lying around, there is one important catch with old Android devices in that they are still old Android devices. Before trusting it, it’s vital that the device is factory reset or has all unnecessary apps removed and is kept off the open internet (like all other smart home devices). Only give it the permissions it actually needs, and you’ll be singing.