Hardware¶
Nothing here is required all at once: build the base station, then add whichever sensors fit your site. Prices are rough street prices (mid-2026, USD) for the cheap-clone tier; brand-name versions cost more. Product links are Amazon affiliate links (they help fund the project; buy anywhere you like).
| Role | Part | ~Cost | Notes |
|---|---|---|---|
| Base station | Raspberry Pi 4 (2GB+) | $45–99 | Runs the whole Docker stack. A Pi Zero 2 W (~$15) works for light loads. |
| microSD 16GB+ | $6 | Or boot from USB/SSD. | |
| Base scanner radios | USB BLE adapter | $8–12 | Any BlueZ-compatible dongle; many Pis have BLE built in ($0). |
| USB WiFi adapter w/ monitor mode | $10–15 | Needs an mac80211 monitor-capable chipset (e.g. RTL8812AU, AR9271). Onboard Pi WiFi usually can't sniff. | |
| WiFi/BLE sniffer node | ESP32-C3 SuperMini | $2–3 | Cheapest sniffer; one radio per board (WiFi or BLE). Onboard PCB antenna is often detuned on clones → shorter range; prefer u.FL/external antenna if coverage matters. Deploy several. |
| ESP32-WROOM-32 DevKitC | $3–5 | Dual-core alternative, no real advantage for sniffing. | |
| Vehicle sensor node | GY-271 (QMC5883L) magnetometer + any ESP32 above | $2–3 | I2C module; detects the magnetic signature of vehicles within ~2–5 m, no phone required. |
| Vibration sensor node | Piezo disc (27 mm) + 1 MΩ resistor + any ESP32 above | <$1 | Glued to a door/gate/fence; classifies knock vs sustained shaking on-device, ignores wind. |
| Contact sensors | Reed switch, PIR (AM312), IR beam-break, float switch | $1–8 | Wire straight to a Meshtastic node's GPIO, no custom firmware. |
| Off-grid / LoRa node | Heltec WiFi LoRa 32 V3 | $12–18 | Only for sensors/alerts beyond WiFi range. Runs Meshtastic (or MeshCore/Reticulum stacks). |
| 868/915 MHz antenna | $2–5 | Match your region's ISM band; never power a LoRa board without one. | |
| Reticulum relay host | Pi Zero W + RNode | $15 + RNode | Runs sensors/rns_field_relay.py for the LXMF backhaul path. |
| Power (per remote node) | 18650 cell + holder, or USB PSU | $5–15 | Solar + LiPo for true off-grid; a phone charger indoors. |
Build tiers¶
- Minimum viable tripwire: a Pi with built-in BLE running the base scanner. Zero extra hardware, real BLE MACs, limited to the Pi's radio range.
- Property coverage: add ESP32-C3 sniffers around the buildings, a GY-271 at the driveway, piezo discs on gates and fence runs, reed switches on doors.
- Off-grid perimeter: Heltec V3 nodes carry far sensors over LoRa; RelayFabric carries alerts out the same way.
Reality check: phone MAC randomization means every tier detects presence, not identity, so buy for coverage (more cheap nodes), not for a fancier single node.