On of my favorite iPhone feature is push notifications. However, only a few applications use these well (ESPN ScoreCenter, AP mobile, Twitter, etc.) and I’ve always wished I could write my own without creating a full blown iPhone application. Enter a simple application called Prowl. Prowl is a Growl client for iOS that pushes notifications to your iPhone, iPod touch or iPad with a simple API. To send yourself custom push notifications, you’ll first need to buy Prowl for your iPhone (around USD$2.