Alarm Relay is reliable, they answer the phone when you call, and they do what they say. They also are a bit on the expensive side, but cheaper than many, like ADT. They do support DIY, but they don't do a lot of hand-holding, so as long as you know what you are doing, they are good. Here is an example. When I first got setup up, I had my panel send open/close reports as I had that with NextAlarm. Note I am using cellular only. About 7 months later they called me up to turn it off, saying that feature costs extra. I understand that, but it took them 7 months to figure it out.
Also, note, Alarm Relay seems to call for EVERYTHING. Battery low, they call. Trouble anywhere, they call. Sometimes its a bit annoying, like when your wireless battery gets weak, as they always do at 3am, they will call and tell me, but the panel has already told me, so it's a duplicate.