Verisure
About the vendor and its products
Verisure is a security and alarm company operating in different countries, with a strong presence in Scandinavia. The company also provides some smart home components integrated in the alarm systems, and I have included it here since we have our alarm system from Verisure. Smart solutions/components offered (notice that since the product offering differs from country to country, the selection available in your area might be different from this list (this is certainly the case for Norway, with a list of products available here on the Norwegian version of this Verisure page):
Alarm systems, combining physical products and services
Various sensors/overvåkningsenheter, like smoke detector, shock sensor detector, and perimeter detector
Alarm components, like siren, panic button, and remote control
Surveillance camera
In some markets, there is also a smart plug, heat pump controller, and smart door lock module
The alarm system and its components are controlled from a Verisure app, one version for systems based on a so-called VBox and one for other types of systems. I cannot say for sure about how this is in other countries or systems not based on VBox, but at least in Norway, Verisure has decided not to open up for integration with any other platforms. There is, though, a community-created Verisure-plugin for Homebridge (as well as for Athom Homey), which means the components to varying degrees can be integrated into Apple Home.
Our experiences
We have an alarm system from Verisure, with a number of different components. These work well in their intended use integrated into the alarm system, and they somehow work in the smart home when I managed to integrate them through Homebridge, but this is far from perfect, with needs for resetting and long response times. I am critical of the strategy of isolation chosen for this system and this is the reason why I have not acquired any more components from Verisure, but instead gone with cameras/sensors from other suppliers that realize that customers want platform openness. From the spring of 2019, I started and completed a process to replace the Verisure components with other alternatives.