I love my Ecobee thermostat, but their servers are down constantly. I would never trust them to run my home security. They build great hardware, but they need to hire better software developers.
Personally I have a very traditional Honeywell alarm system with the metal box in my basement. It is an Ademco Vista 20p. That is pretty much the #1 alarm device in the world. But it's not "smart," it's very traditional where when there is an alarm it uses a phone line (mine is cell phone) to call the alarm company. I prefer this. Hubitat is great, I really love it, but alarm systems are held to a higher standard. UL has specific requirements for alarm systems that Hubitat doesn't have to follow. If my house were burning down I want to be very sure that the fire department gets called so the traditional alarm makes me feel safer.
But I want the best of both worlds. I want it in HE too! So I use this device, http://www.alarmdecoder.com/ it basically connects that traditional alarm system to a Raspberry Pi that I can tie into Hubitat. I have virtual devices for each of my sensors (door, window, fire, carbon monoxide, glass break, motion) that I can monitor in Hubitat. There's a slight delay because it is going from RF to alarm wiring to a raspberry pi to LAN, to Hubitat... but a delay of maybe 3-4 seconds which I can tolerate. So I get a traditional alarm system that doesn't depend on Hubitat, but I can also control and monitor it from Hubitat.