HESI

Recommend that you look at better options c/o Angie's List.
From the tech side, we had the usual quirks with HESI as I'd expect from a security service.  The occasional blip in the system.  It's really the service from this group that's at issue.  VERY nice people, but the service aspect appears to be an afterthought. Leaving HESI is an expensive and painful process as well.
1)   Phone calls sometimes take days to return.  Have an issue with billing or a question about your account?  Call between the hours of 9 and 4.  Someone might be there to take your call.  Otherwise hold off until the individual gets around to it.  For example, my call on Tuesday was returned today (Thursday).
Issue here is that this doesn't give me, as a customer, much confidence in how the security monitoring process is handled at HESI.  I never had to use it...but the lax approach to business and customers made us feel very uncomfortable with our home security.
2)   "Gotcha!" contracts.  Pointing out here that HESI has an automatic renewal built into the contract.  No notification - you simply get signed up on an automatic basis.  Our three-year contract became a lifetime contract under HESI with a "...you signed this contract and it states that you need to pay a $75 cancellation fee" point when we wanted to call it quits.  
I was simply moving on to another company and they hit me with that "Gotcha!" tone and the renewal message.  Save yourself the $75 lesson.  
3)   Slow Repair Service.  Back again to the issue that this company seems to be extremely lax and/or understaffed.  We had an electric surge hit our system - causing it to no longer monitor and to "BEEP" every night at 3AM.  The process to get someone out for repairs and to reset the system has taken two weeks.  No service and a wake-up BEEP...BEEP... every night.  
Troubleshooting was that I needed to buy a $35 battery from Radio Shack and to replace it myself.  (No change)  OK...wait 36 hours.  (No change)  OK...we will send someone out but it's going to cost you $35 per hour.  Repair was scheduled two weeks after the first system shutdown and the nightly BEEPs.
4)   Challenging Process to Leave  Surprise from a three-year contract that is actually an automatic annual renewal contract.  To leave, you will also have to send them a signed statement saying that you no longer want the service.  For your protection.  They certainly seem to be good at protecting their right to charge customers.

The new home I purchased had an alarm system installed by a different company that the builder no longer uses. The builder recommended HESI for monitoring service. Their sales rep. came out on time and explained all of my options for contracting with them to monitor the alarm system/fire alarm in my house. An appointment was then made for the service technician to come out to the house and get everything set up with the alarm. I wish I could remember his name because I was extremely impressed. He went up in the attic and noticed that the fire alarms in the garage were improperly wired to the rest of the system. He spent 4 hours fixing the installation to ensure the system worked properly. I have accidentally tripped the system a few times in the past year and every time their monitoring station called my home phone within minutes to say they had an alarm activation and to make sure everything was okay. At first I was a bit skeptical using a company that wasn't a national well-known company, but so far I have got my money's worth from this local company. I would definitely recommend them.