Glass breakage detection is not overkill. Between survellience cameras and a home security system, you are trying to accomplish two main things. Identify the perp or perps, and try to prevent them from entering your property at the earliest point. Glass breakage detection helps aid in the earliest detection on the alarm side. Properly setup, they are a valuable tool in your system. If your town ordinance allows it, also look at an exterior siren with strobe.