Universal Bluetooth Smart Security USB Padlock - Black
This tough lock can be used in the same way as any traditional padlock, but is entirely operated and controlled by your Smartphone.
Just download the 'KOLMON' APP from either Apple or Android App store. Once you've created an account you can, set up your lock, add Users and monitor the battery level of the lock.
The auto- unlock feature works from 3m and stays working with the 500mA battery.
Compatible with Bluetooth 4.0 and up.