"Notifo is a mobile notifications platform empowering developers to build their own services with a scalable and reliable notifications API. The Notifo API is a simple and affordable way to add notifications to any web app or project." (Description is from the Notifo website)
I create this Objective-C library last year in my spare time. I've just added a test interface and simplified the code by using blocks when making Notifo API calls. You can download the library here. Enjoy!