Alarms for houses, business, pools,  or any  civil structures that need protection is a must in these days.. Many persons will have them to have a peace of mind, even living in safe places like gated community, or buildings with guards.. The majority of the persons worry about two things when they got a new systems, that if they will be setting their own alarms, and what the alarm installation will do to their house.
 Alarms has been upgrading continuously.  You do not have to worry if the alarm installation will damage your walls, the latest alarm system are wireless, they have to be hooked up to a power line and a phone line, so there is almost no damage to your home.  
If you still think to much about the possible damage that can be made,  ask the company that you have chosen to tell you what the alarm does, and what are they going to do in your house.  Usually you will see new boxes around your home near your doors, if you are getting a home alarm, and possibly new lights outside or small tabs on your windows, but it all  depend on what you have chosen. Otherwise, you should not see any damage or anything overly unsightly.
If what the company tell you about the alarm installation do not satisfy you  completely, you can be there when they are doing the installation.   In this way if there is something you do not like, you can talked to them right away and fix it  as soon as possible.   The other thing that can be beneficial when you are present during the alarm installation is that it  will be  helpful in your understanding of what the alarm does and how it works. This might mean less problems for you in the future. In this way  you can decide then and there if you have gotten enough features on your system, or if you feel something is lacking and you wanted to add it.   In this  way, you can make your  additions right away -in many cases- without having to wait for them to come back later.