A local alarm built with inexpensive Zigbee sensors, Home Assistant and Alarmo offers a cheaper alternative to professionally installed systems and recurring monitoring fees.
I grew tired of the usual trade-offs in home security: paying a large sum for a professionally installed alarm, then adding a monthly monitoring fee on top, or buying a cheaper DIY kit and still depending on a vendor’s cloud. In the case described by XDA Developers, the answer was to build a private system from inexpensive Zigbee sensors, Home Assistant and the Alarmo integration, keeping the whole setup local rather than tied to a subscription platform.
That choice reflects a broader cost pattern. Homebuilding.co.uk says basic DIY security installations can start at about £250, while professionally fitted systems commonly begin around £500 and can climb far higher once sensors, cameras and installation are added. In the US, Vivint’s 2026 pricing guide puts equipment for a home security system at $130 to $1,500, with monitoring typically costing $8.49 to $55 a month and installation ranging from nothing to $199. Other industry guides quoted by the companies place professional monitoring anywhere from roughly $10 to $60 a month, depending on the service tier.
The attraction of the XDA approach is not only price. Home Assistant is designed to run on local hardware, from a Raspberry Pi to a home server or NAS, and can connect to thousands of devices without sending every event through a third-party cloud. Alarmo adds alarm-style functions such as arming and disarming modes, schedules, geofencing, notifications and siren triggers. For anyone already using Home Assistant to manage lighting, heating or cameras, that means the alarm can become part of a wider automation system rather than a separate subscription product.
The article also makes a technical case for Zigbee over Wi-Fi. Zigbee is a low-power wireless protocol suited to sensors, switches and locks, and it is less demanding on batteries than Wi-Fi. That matters for door and window contacts, which may need to last for years on a single pair of batteries. Homebuilding.co.uk notes that wireless systems and flexible, expandable designs are often the best fit for homeowners who want to secure key entry points first and add components later. Powered Zigbee devices, such as smart plugs, can also help extend coverage by acting as repeaters.
In the build described by XDA Developers, Sonoff hardware was used for the network backbone and for most of the sensors, including door and window contacts and motion detectors. The total came to about $185, with much of that cost attributed to a wall-mounted display used as a keypad. A four-pack of Zigbee contact sensors was said to cost about $40, while a motion sensor was about $16. The result, according to the piece, was a local alarm system with no cloud dependence, no monthly bill and no reliance on a single brand staying in business.
Disclaimer: This content is intended for informational purposes only. Readers are advised to exercise their own judgement, conduct due diligence, or consult a qualified expert before acting on any information provided.
