a. Actually, it can work better than a door bell for the following reasons, if your visitor can scan your 'Notify-Me-Card':
i. It doesn’t need electricity.
ii. As the account owner, you can hear your email device notify you with a sound, vibration, or flashing light wherever you are.
iii. You may be visiting a neighbor or working in the garage or basement, out of range of hearing a door bell.
iv. This is perfect if you have a hearing disability.