$100 per year
These take a little longer than test strips to use, as the chemical reaction has to take full effect, but most reagent test kits offer a wide range of variables the user can test.
Hand-Held Electronic Sensors
$200 - 500
These sticks can measure a variety of variables very quickly and precisely. The do require you to be there to hold them and some people have issues calibrating them.
Combining scalability and sensor customization with affordability, the OsmoBot stands above the competition as hydroponic farmer's best option for monitoring his/her system. Call us biased, but we honestly believe we stand head and shoulders above the competition.
The OsmoBot's closest competitor in terms of price, Bitponics launched a successful Kickstarter campaign in 2012. Since then, there has been little public progress with their product. Their base unit monitors: pH, water temperature, light spectrum, air temperature, and relative humidity.
According to their website, the GroBot offers a turnkey way to fully automate a small hydroponic grow room. It will mix all of you nutrients and allow you to be completely hands off from your hydroponic system.
Agrowtek GC Pro
Advertised as more "flexible" than a plug and play system like the GroBot, the Agrowtek GC Pro monitors all of the necessary environmental variables for hydroponics, like CO2 and humidity, and has the ability to monitor water variables, like temperature, but they require additional purchases.
Smart Bee Controllers
They have a great promotional video on their website. This product seems to do all of the environmental monitoring and controlling a small, grow room would need. What's lacking is any way to monitor reservoir conditions. It costs an additional $700 to just get information about temperature and moisture content in the growing medium.
The iPonic system monitors all key environmental variables: CO2, temperature, humidity, and light spectrum, and can automatically turn on backups for the user to control the environmental grow space. It has no abilities to monitor any variable in the water.
$10,000 - $1,000,000
In terms of features and flexibility of applications, Argus Controls leads the hydroponic monitoring industry. They build custom systems for any greenhouse application and can control all aspects of a hydroponic operation from nutrient dosing to venting. The disadvantage with Argus is that these features come with a cost and only the largest, highest revenue farms can afford their services.