High Performance Wireless Proximity Tracking Devices and Alert: 6 Months Long Battery Life, -40F(-40C) to +185F(+85C), Small Size, 30m/100ft Reliable Tracking, Alarms Monitor/track two devices' distance/range/proximity and temperature Long Battery Life (6 months 24x7 non-stop running), Good Penetration to Obstacles (walls, trees, snow, dirt), Life-threatening Temperature Alert Small Size, Light Weight, Wide Operating Temperature Range (-40C/-40F to +85C/+185F), 30m/100ft Reliable Tracking Range, Adjustable Monitoring Ranges Single Standard "AAA" Battery, Works inside purse, backpack, building, tunnel, boat, forest, cave, dirt, debris. Stand-alone (No Subscription or Monthly Fees) Certified for Use in Safety, Security and Rescue in the USA and Canada, No need to see the sky like GPS or to stay within fixed WiFi or cellular coverage. Made in Canada