Has the door been left open? Is my loved one not answering the phone and in trouble or are they just out at the moment? Contact Sensors allow TruSense to determine if a door has been left open too long and will also combine contact sensor status with motion to determine if they are home or away. Place TruSense exit sensors on exterior doors and, in combination with activity sensors, know when your loved one leaves their home. You can also receive an alert on your mobile phone for instant peace of mind.