ADT Are really, really expensive compared to what is out there. They use hard, pushy door to door sales staff who are on commission only. They are often backpackers and have no real idea of what they are doing.

I've been a customer for more than 10 years. ADT monitor my house alarms on a back-to-base basis with call-outs, etc for alarm activation.
I only ever have phone contact with them and they are quite helpful with questions. I have had no problems at all but increased peace of mind when I am away.
A slight prbelm was that when my battery went flat I was quoted $800 for a technician to replace it. I though that excessive and said I would close my account rather than pay an outrageous fees. The helper on the phone then gave me a reduced fee of $300 if I agreed to sign up for a further two years. So, that was pretty ok. In the end the technician took less than 15 minutes to instal the new battery.
When my keypad malfunctioned, the fee to replace it was far more reasonable.
So, if you require an alram system (emergency, break-in, fire, panic switch, etc) ADT are a good company to deal with.