Push, or server push, describes a style of Internet-based communication where the request for a given transaction is initiated by the publisher or central server. It is contrasted with pull, where the request for the transmission of information is initiated by the receiver or client. http://en.wikipedia.org/wiki/Push_technology
Push notifications work on most smart phones, but recipients have to download and install an app compared to just putting their number into a list. There are people that don't have smart phones and many people disregard/disable push notifications - unless its an SMS.
In theory, push notifications seem to be a cheap and elegant way to prompt a mobile user at the right place, at the right time, with the right information. In practice, however, Apple’s and Android notification channels are flooded by marketing messages as application developers trick users into granting permission to send alerts, and then often abuse that permission.
“the basic problem with push notifications is they are used an email replacement. I can see marketers and growth hackers getting all hot n’ heavy realizing that they can now send the weekly “people you should follow” email that nobody reads as a push notification to your mobile device.”
The result? Many mobile users doggy-paddle aimlessly through an ocean of push notifications or some learn about OS-level settings and disable them selectively (or altogether). And, that’s what usually happens,
http://techcrunch.com/2013/10/13/the-precise-art-of-mobile-push-notifications/
They are not reliable! There is no guarantee that push notifications will actually be delivered, even if the APNS server accepted them.
"Push notifications should not be used for critical alerts because the message will only be delivered if the device has wifi or cellular [data] connectivity, which is why we recommend combining push with another alerting method such as e-mail or SMS for our server monitoring alerts.
https://blog.serverdensity.com/how-to-build-an-apple-push-notification-provider-server-tutorial/
As far as your server is concerned, push notifications are fire-and-forget; there is no way to find out what the status of a notification is after you’ve sent it to APNS. The delivery time may also vary, from seconds up to half an hour.
Also, the user’s iPhone may not be able to receive push notifications all the time. They could be on a WiFi network that does not allow connections to be made to APNS because the required ports are blocked. Or the phone could be turned off.
Push notifications require the app to be running in the background most/all of the time. This tends to significantly shorten battery life and have a negative affect on overall performance.
APNS will try to deliver the last notification it received for that device when it comes back online, but it will only try for a limited time. Once it times out, the push notification will be lost forever! See: http://www.raywenderlich.com/32960/apple-push-notification-services-in-ios-6-tutorial-part-1
Telegram is probably the most popular Free push notification service. Telegram provides a very comprehensive feature set and is a clear, first choice alternative if a free push notificaton service is preferred to a professiona SMS service such as SMSBroadcast https://telegram.org/
The Skoolbag app provides “Free Push Notification Alerts” (it does not include or provide a method to send SMS messages).
"Any content added to Skoolbag can be pushed as FREE instant push notification messages, such as news, events, newsletter posts, last minute cancellations, etc. Plus you can categorise the push alert to target years, classes, subjects sports teams, drama classes, etc. A great replacement to school SMS."
In other respects it offers no additional features compared with a standard web site/Content Management System. Skoolbag extends rather than replaces what is already available on a standard DEC website.
COST:
Remind is a free, safe, easy-to-use communication tool that helps teachers connect instantly with students and parents.
Teachers, students, and parents can streamline their login or account creation by using their Google credentials. If your school uses Google Apps for Education, it’s easy to connect your GAFE (Google Apps for Education) account!
Teachers may use 'classes' to message students or parents or both. Each teacher can add up to 20 classes.
Over 35% of k–12 teachers in the US, and 1.5 million teachers globally, use Remind to connect instantly with students and parents.
NOTE: There is no way to upload subscriber information and automatically add them to a class. Students & parents MUST opt-in and understand the types of messages that they will receive.
Any user who chooses to install the (Free) official Twitter app has the option to receive push notifications. The options are highly customisable and can include notifications for almost any event, such as when a particular user tweets or when someone mentions you in a tweet, and more.
The twitter app is robust, under continuous development and supports most modern mobile devices.
Twitter gives you the option to choose what notification(s) you wish to receive.
Send push notifications to iOS, Android, and Fire OS devices when you publish a new post.
Straight from your WordPress site, in real-time: http://codecanyon.net/item/push-notifications-for-posts/6868260