Bluetooth Fuel Tank Monitoring for iOS
A Bluetooth-first iOS app that lets site operators track and control every gallon in their on-site tanks, replacing expensive hard-wired telemetry hardware at a fraction of the cost.
FMS lets operators of on-site fuel tanks — construction sites, farms, fleet yards, generators — track fuel levels in real time and act on them, without the cost or install complexity of traditional fuel telemetry hardware. A Bluetooth Low Energy sensor on the tank and a native iOS app that reads it directly turn a multi-thousand-dollar install into something an operator sets up themselves in minutes.
Manual dipsticking doesn't scale, and telemetry systems cost too much.
Small and mid-size operators still walk out to physically check tank levels — error-prone and zero warning before a tank runs dry. The alternative is a hard-wired SCADA-style system: a licensed install, a proprietary telemetry box per tank, and an ongoing cellular data-plan fee wildly disproportionate to the problem being solved.
- Direct sensor communication over Bluetooth — no gateway hardware
- Real gallon-level accuracy operators can trust enough to schedule refills against
- Remote visibility across sites from one operator, one app
- A single developer could own the whole build, start to finish
How we built it.
CoreBluetooth for direct sensor communication
The iOS app connects directly to each tank's BLE sensor using CoreBluetooth, reading fuel level and temperature without any intermediary gateway device.
RESTful API layer for sync and multi-site visibility
Once the phone reads a tank locally over Bluetooth, it pushes the reading to a backend over REST, so tank history and multi-site dashboards stay available.
Offline-first reads, online sync
The app reads and displays sensor data locally first, then syncs to the backend when connectivity allows — built for a dropped or weak Bluetooth connection.
Single-engineer-owned build
With no dedicated backend or hardware team, the system was kept to two moving parts — the iOS app and a thin REST API — rather than a distributed backend needing a larger team.
The solution.
Direct Bluetooth tank reads
The app pairs with a tank's BLE sensor via CoreBluetooth and reads fuel level directly — no proprietary telemetry box between the sensor and the app.
Multi-tank, multi-site dashboard
Every tank an operator manages is visible in one app, with the REST layer syncing each local BLE reading so an operator can check any site remotely.
Offline-first reliability
The app is built to read and display the last known state clearly, and sync new readings as connectivity allows — rather than failing or showing a blank screen.
Threshold-based awareness
Tanks are tracked against low-fuel thresholds so operators can see, at a glance, which sites need a refill.
A single, developer-owned system
The entire product — iOS app and backend API — was built and shipped by one Cosmoxyn engineer, end to end.
Outcomes that shipped.
Operators could see real gallon-level tank data without installing a single piece of proprietary telemetry hardware, and multi-site operators gained one dashboard view instead of manually checking each tank in person. The cost structure of tank monitoring shifted from hardware-plus-monthly-data-plan-per-tank to an app on a phone operators already carry — proving a single engineer can take a hardware-adjacent product from concept to shipped App Store product without a dedicated hardware or backend team.
What we took with us.
- 01Earlier field-testing across a wider range of tank enclosures — BLE range and reliability varied more than lab testing suggested once real metal tank housings were involved.
- 02More proactive threshold and alerting configuration — early users wanted smarter default low-fuel thresholds per tank type, which matured after initial launch.
- 03Native Android support considered sooner for multi-site operators with mixed device fleets.
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