My solutions don’t exclusively rely on the ecobee3’s remote motion sensors (which are not meant to be used for real time HA scenarios as there is a huge time lag: at least 30 minutes). At my home, I prefer to use any reliable ST connected sensors.
See this thread for more details:
P.S. You’d need MyEcobee device as my smartapps leverage its unique set of features This is the most comprehensive ecobee implementation in ST.