Pushpad

 Pushpad  is a web push notifications service.

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:

Pushpad Express
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.

Pushpad Pro
A customizable white label solution made for developers/large projects who want to add push notifications to a website or web app. Choose Pushpad Pro if you are looking for a Backend as a Service and you want to subscribe users to push notifications directly on your website using the Javascript SDK.

Pricing
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.

Integrations
The service provides a free WordPress plugin with documentation.

Indieweb Examples

 * is experimenting with using Pushpad Express on his primary site in conjunction with their WordPress plugin.