Pushjet is a open source push notification service.
Pushjet is a simple open source push notification service designed with freedom in mind. No user accounts are required and all notifications are destroyed on the server once received by the client. There are no user accounts, instead it's bound to your device's unique identifier. The application allows the user to self-host a notification server if desired. Sending and receiving notifications is done through a public/private key system.
The source code can be found at https://github.com/Pushjet