Design an Aquarium Levels Monitoring Device with Cloud based WebApp

I would like to design an aquarium monitor device that is not only cost effective but is also just as accurate as the more costly industrial monitoring devices from companies like HANNA and PINPOINT. The sensors can be sourced, but not all are cost effective, and in most cases the retail price of just the probe is more then I want the whole product price to be at. I want to create a base device. From that device, I want to be able to monitor both saltwater and freshwater parameters needed depending on what probes/sensors are connected. The device needs to communicate with wifi routers in the users home and be able to update a cloud server database with the current readings from the sensors, also display those readings in an app accessible on the Android and IOS. My idea is to have our pcb board design, not use some arduino system. I want the device to be a magnet on one side with the wifi device, and the other side with the sensors goes in the water. It might actually even be able to serve as a glass cleaner as well. The base "freshwater" device monitors TEMP, and PH with internal sensors built inside the device, not hanging from device as a probe would. It's aimed at the aquarium user with an existing freshwater aquarium (in other words, a cycled tank [read up on nitrogen cycle if you still don't understand). New Aquariums go through whats called the nitrogen cycle. Normally aquarists are testing for ammonia the first week or two, followed by a spike in Nitrites, and then as the nitrogen cycle completes the Nitrates will begin to rise. Nitrates are the end product you test for. Nothing gets rid of Nitrates except for water changes, and a good refugium with lots of macro algae. Alerts will be setup so if levels go above recommended safe levels for fish, recommendations will be made to offer products from affiliated website retailers. There is currently a device that measures TEMP, PH, and AMMONIA for $200 [login to view URL] They sell the wifi device separately for another $250 [login to view URL] The device uses a replacement sensor that needs to be replaced every 30 days. The 3 pack costs about $34 [login to view URL] This device above does NOT measure salinity however. For established saltwater aquariums you need to monitor the following: Saltwater Fowlr device needs to monitor: Temp, PH, Salinity, Nitrate Saltwater REEF device needs to monitor: Temp, PH, Salinity, Nitrate, and Calcium