I’ll start with a disclosure, I’m a co-founder at PushApps so my answer is going to be about why you should consider working with one of the push notifications providers.
I saw Mladen recommendation of Parse, and there are many more great solutions such as urban-airship, pushwoosh, xtify and more. I’m not going to tell you which one to choose.
Of course you can develop it yourself but then you will waste lots of time which you could invest in your main business development - what about special features (scheduling, segmentation etc.)? statistics? OS updates? are you going to support all of it by yourself?
Does it worth the few bucks you can pay to get it all off your shoulders?
think about it… and after that you should visit PushApps