Increased demand for precision agriculture is reflected by a global rise in greenhouse food production. To maximize crop efficiency and yield, commercial greenhouses require live monitoring of growth conditions. Recent advances in open-source hardware allow for environmental sensing with the potential to rival lab-grade equipment at a fraction of the cost. This study introduces a high-resolution sensor package that costs less than $400. Consisting of microcontrollers and small open-source hardware, the sensor package can be deployed on the HyperRail, a modular conveyance system developed in Oregon State University’s OPEnS Lab. The system can then provide data from multiple sensing locations at the cost of a single package. Sensor data, including CO2, temperature, relative humidity, luminosity and dust/pollen, is saved to a microSD card as the HyperRail-mounted package travels throughout the greenhouse. A wireless GFSK nRF connection to a network hub allows the broadcast of a live stream of environmental conditions online. CO2 monitoring efforts are especially relevant to greenhouse management as artificially elevated levels can significantly increase plant growth. Results from calibration in the lab show that the K30 CO2 sensor ($85) can be calibrated to be accurate within less than 10 ppm of industry standard equipment costing up to $10,000. Our sensor package’s instructions, code, wiring, and 3D-printed enclosures are openly-published on GitHub. Addition of an RFID tag soil moisture sensing system is anticipated. Actuators may also be integrated in the future, allowing the system to automatically adjust greenhouse controls (i.e. CO2, water) in response to sensor readings. The affordability of this package can make precision agriculture more accessible in developing countries where conventional monitoring systems are not feasible. Efficient use of resources and the ability to adapt to local challenges with input from the open-source community has the potential to improve global crop yield.