Some recent technologies enable websites to send push notifications to users (if they give their consent) even when they are not on the website. Users don't need to install any app or plugin, since everything relies on browser built-in features (W3C Push API for Chrome and Firefox, Apple Push Notification service for Safari).
The service offers two different solutions which both come with some analytics ability:
The zero setup solution (no technical skills required) to create a channel to send push notifications to users. Creating a new project provides the account holder a link that can be shared with users to let them subscribe to your notifications.
The service is free while in beta and allows up to 10,000 notifications a month for free in perpituity, which likely covers the use need for most personal sites.