I have a lot of opinions on remote monitoring, having been involved with companies that provide it, and doing my own thing, for over 20 years.
Currently aboard I have:
Siren
BRNKL
Boat Command
Maretron
Vesper Cortex
SailLogger
Several other iPad/iPhone systems
Several custom systems including Grafana/Influx
Probably 5 others I'm forgetting that have "remote monitoring" as a side feature
I also have a box of failed companies stuff - probably 8 or 9 different products.
All of them have some core issue that is missing to make them perfect for me. Many of them provide the basics, but require lots of stupid proprietary wiring, or have other limitations. Almost all of the commercial ones are meant for small boats, sub-30 feet, and have limitations there in terms of sensor distance, types of sensors, or just the companies focus on larger boats. Many have huge glaring monitoring holes - like not notifying you if the unit goes offline, no battery backup, and other really dumb things.
I come from the tech world where these sorts of challenges were solved in the late 1990s and early 2000s, and some of these companies have people with similar backgrounds, but haven't solved these irritating holes.
BRNKL uses SmartThings for their remote sensors, but with a challenging implementation that makes it a pain in the ass to maintain. Siren uses their own, and have gone through years of revisions, designed something from the ground up, instead of leveraging existing sensors like SmartThings. As a result, both of these solutions I find inadequate because their remote sensors are unreliable and they have poor notifications when they fail (!!!)
Most of the systems I have seen that work extremely well are hard wired, custom setups that are super expensive, or are based on IoT technologies like SmartThings where those systems have been in much worse conditions in homes and businesses, and the bugs have been worked out.
If you are going to offer something, I would definitely pick your audience. There are sub-slices within the recreational boating world that are wildly different for a product like this. Picking that slice and sticking with it will guarantee some level of success.