Pushover - Real-time notifications on your Android, iPhone, iPad, and Desktop
Pushbullet - Pushbullet - Your devices working better together
Gotify - a simple self-hosted server for sending and receiving messages
QPush - QPush is a free service that lets you easily push text and links from PC to iPhone.
Join - Join is a marketplace for influencers and advertisers to collaborate.
AirMore - AirMore is a cross-platform toolset that can help you manage any Android device wirelessly.