We get push notifications for pretty much anything nowadays, but if you often forget to check your snail mail, Make Magazine shows us how to get push notifications from it using an Arduino and a simple switch.
This is a pretty neat project that you can adapt to almost anything—essentially, it's just a switch that triggers your Arduino whenever your mailbox is opened. If you wanted, you could adapt this to your garage door, your doorbell, or anything else you wanted. It only requires a little electrical know-how, too, so if you're looking for a place to begin working with something like an Arduino, this is probably a good place to start—check out the video to see what I mean.
The video uses previously mentioned Prowl for the iPhone, which requires a PHP server that might take a bit more work (though we've shown you a few ways to do that before), but some commenters over at Make note that you wouldn't need the PHP server if you opted to, say, have Twitter send you a direct message instead of using Prowl. Not only would this rid you of the need for a PHP server, it would also make this work on Android or even a non-smartphone (since you can get text messages from Twitter). It's definitely a neat way to make push notifications alert you to real-world things that need your attention. Hit the link to read more.
Snail Mail Push Alerts [Make]