SmartThings is not reliable enough for a primary security system. That’s not just my opinion: The company says so themselves in the product usage guidelines:
- Data accuracy and consistency from SmartThings sensors, including those provided by SmartThings directly, resold by SmartThings, or supported by SmartThings, is not guaranteed. Therefore, you should not rely on that data for any use that impacts health, safety, security, property or financial interests. For example, because temperature readings may vary significantly from reading to reading on an individual device, between devices, or over time, those readings should not be used to control heating and cooling in environments where food spoilage, health risks, or damage to physical goods could occur. Alternately, presence data from SmartThings devices or mobile/Smartphones can vary in accuracy, and therefore should not be used to control access to secure locations without secondary authentication.
There are a lot of things you can do that can help improve the day-to-day reliability, but the system as a whole continues to have various inconsistencies and minor outages. It’s very flexible, it has a lot of versatility, and it supports many different devices, but it just can’t compete for reliability with a purpose-built security system, even an inexpensive one.
I’m sure you will get many suggestions for how to reduce some of the issues, and adding more repeaters may well help, but it just is what it is.
If you are looking for a primary security system, I would look at something which was designed for that purpose. Ring security, Abode, Nest Protect, Simplisafe, and LifeShield are all worth considering at the lower end of the price range. Frontpoint is another candidate, but more expensive and requires a long-term contract. Each has different pluses and minuses, but you can find many reviews comparing them.
(The ADT/SmartThings dual logo system had a lot of good features, but since ADT bought lifeshield the SmartThings model appears to be an end-of-life system now and it can be difficult to find the devices for it.)