I had to configure a sort of... inverse debounce on a cheap motion sensor I bought. It has to go off more than once (in a short time period) before the alarm is triggered.
Elk systems have a similar option called (iirc) cross monitoring. When enabled, two motion zones must trip within (e.g.) 2 minutes before the area will alarm. They could be sensors covering nearby rooms (and catch someone walking from one to the other) or have different angles of the same room. Either way, it's quite resistant to false positives.
