I just got an alarm in, when my house was built 18 years ago. I didn't sign any contract for maintenance etc and it worked just fine. Probably saved about €100 per annum in not having it serviced so it has paid for itself in the savings made. It started giving gip last year and would start ringing intermittently. I disconnected the battery inside the house.
It probably just needs a good service at this stage and it will be right as rain. I am just weighing up the pros and cons of a house alarm and whether it is worth having one at all. My house insurance is about €500 per annum. Probably saving about €50 per annum by having a house alarm.
Personally I think that house alarms are more of a nuisance in the long run.