Personally, I am not a fan of monthly paid security systems. Why? I have a police friend that told me when a residential alarm is triggered that call is one of the lowest priorities to respond to. That is when the ALARM COMPANY calls the police. There are times that it can take 30+ minutes for them to respond to that call if they are busy at that moment.
Another thing too almost all security companies (ADT, simply safe, digital life, brinks ect..) use proprietary software/hardware that doesn't link into any other 3rd party system. Why dont it? It's because those companies offer their own camera systems and services that they want to push on the consumer to buy.
I had digital life by ATT, after I cancelled all my equipment was useless because the radio bands the equipment used for the door sensors and motion sensors and smoke detectors was a proprietary band and only can be used by ATT and nothing else. (Except their cameras, I was able to finally unlock them and get it to work with BI)