I want my existing MODBUS network to fire off an SMS the instant our ammonia reading crosses a set limit. The only alert type I need right now is a threshold alert; status updates or generic error messages can wait for a future phase. Scope • Poll the ammonia sensor register over MODBUS RTU or TCP (my gateway supports both). • Compare each reading against a user-defined threshold (ppm). • When the value exceeds that limit, send a single SMS to one or more numbers via either a local GSM modem . Deliverables • Ready-to-run source code or flow (Python script, Node-RED flow, or similar). • README covering dependencies, setup, and how to adjust thresholds or phone numbers. • Step-by-step test plan and remote hand-off session so I can watch the alert fire in real time. Acceptance criteria • Sensor values are polled at the interval I define and logged locally. • An SMS containing the ppm value and time-stamp arrives within 5 seconds of the threshold being breached. • No duplicate messages while the reading stays above the limit; a fresh alert is generated once it falls back and exceeds the threshold again. If you can leave clean hooks for adding temperature, pressure, or voltage thresholds later, all the better, but the immediate goal is dependable ammonia exceed alerts. Let me know which language or framework you prefer and how quickly you can have a tested solution in my hands.