Do a quick check on Google search engine : You should get a large number of hits from outside the vendor's own website! And, with global attendance.
Look on YouTube for a good number of videos on - product, installation, troubleshooting, setup, tutorials etc... Again, see if a large number of these videos are posted by a multitude of companies/people from around the world and by outside the vendor's establishment!
You should see a large number of reviews on several online platforms (good, bad & ugly - but a large number of them - from all over the place, not restricted to your geography!)
Look for skills on Amazon Alexa, Google Assistant & Apple Homekit/Siri - ALL three of them; You should be able to easily integrate - with every new revision/version/model of the product getting launched in that global ecosystem
See how many User Groups and Forum are available online and if they are vocal/prominent in their discussion... It will be good to see global adoption & country-specific groups
Support services around these suite of solutions should be online, easily accessible & there must be an escalation mechanism feasible in the public domain; It should not be niche & speciality-driven; Do you pay 'AMC' for washing machines, TVs, Amplifiers, Refrigerators, cooking range (all of which have higher probability of failing or producing incidents)....? Then why do it for these IoT products?
Is it listed with services in IFTTT? Not that IFTTT makes it robust or complete in anyway - but it is a good starting point!
A simple yet effective check is to look for a well designed & graphically enabled app/interface on both - iOS + Android, BOTH! It is easier, cheaper and quicker to get it on Android based systems... But, any meaningful product development in the space of residential solutions is not at all about being easy in rustling up a device or going quick to the market with a small expense to justify your commitment!
Another, common give-away of fly-by-night operators with shoddily stitched products in this disorganised market (ever wondered what is the litmus test for being an IoT product solution, where everyone and anything can go with that moniker?) - spelling mistakes in their product information brief & on their website/webpages! Not to assume that those who dont make these silly mistakes or have perhaps only spent money in getting good graphic designers working on it - are necessarily better! You have 10 more points herein, to tick!
How often does the firmware of your "IoT" products get revised/updated in a year and does it continuously, throughout its lifetime, get new extensions or plugins for connecting to multiple platforms or devices/appliances of use at home? How many different platform & application providers adopt this technology connect for making themselves a part of this network?
And it is not at all the norm to pay for upgrade of firmware/softwares - which should happen OTA, automatically with all the security framework of these systems being in place; And it is a thing of the past to pay for any sort of "subscription" to any of it... Anyone trying to propose complex product costing models is only doing jalebi-work!
When you find the mention of these products mainly on trading platforms and primarily through webpages of online product aggregators - you should pay extra attention to the above checklist and perhaps even if any one of the above dont fit good, it is unlikely that the product solution is likely to be available for any good use, even after just a few months!
Make sure that your IoT solution provider - has an appropriate app & user interface... certainly not just opening a 'local webpage' from within your premises to manage the devices/applications at home!
And, most importantly - realise the fact that these are emerging technologies and they are still a fragmented lot. There is a lot of development happening, standards are evolving, products are getting launched every day, new applications are being addressed and a lot of collaborative work is happening in the ecosystem - where everyone needs to be connected and working togther in many ways! Hence, you need a technology solution provider who is mindful enough to have an online support alongwith an efficient helpdesk / support technicians who can see your emails, login and check... and everything is done from their portal or by simple emails sent by customer directly... There shouldn't be too much dependence on local dealers and Customers should not be made to run around, chasing multiple people...
Smart solutions & products require to be used effectively and it doesnt just end with installation! Many times, an appropriate platform is essential for realising the larger benefits of such IoT solutions and to make Smart Homes out of them - with practical applications