On the $15 plan they'll call 2 listed phone numbers first before calling the police. There's a $20 and $25 plan that has more features like text messages and smart phone app and the web interface for setting and monitoring the system. The cheapest way to get started is to buy a refurbished system and apply a discount code and buy everything at once as the discount for buying a system applies to the added items.
My biggest annoyance with the system is the remotes don't have a "home" button, so if you leave the house with someone else still at home, and you want to leave it in "home" you have to open your exit door and press "home" on a keypad, then leave and shut the door. You can't leave and shut the door then press "home" on the remote, as there is no such button. You could place a keypad outside the door, (picture garage use case) but that's less secure. Because of this for my use case 2 keypads are needed, one near each common exit, to allow people to leave the system armed in home mode when they leave and other people are still in the house. You could get around this by paying for the smart phone app plan level and use that, but I try to minimize recurring expenses.
We did have to fiddle with the motion sensor arrangement and sensitivity when we got a pet, but at least we know the motion sensors work, and they called us before the police so no false report issue.
As an earlier poster said, the communication between the keypads and base station are not encrypted, and could therefore be subject to an attack replaying transmissions to disarm your system. Personally, I'm not worried about it.
They have camera offerings now, which they didn't when I setup my system. I have a separate camera system, RSC, security through obscurity, locked doors, and property insurance. Good luck, burglars suck.