iPhone/iPod Question: what us that strange exclamation point icon for?

A few weeks ago I installed androidlock from cydia and noticed that I started to see an explanation point next to my battery indicator like the one pictured here.

Any jailbreaker will tell you that when your phone acts "strange" you worry because it could mean a restore which can lead to complications and a possible dead iPhone (referred to as a "bricked" iPhone)

I thought that it may refer to my battery itself which worried menbut apple has nonsuch article referncing this icon.

From research online which only brought up one page these indicators seem entirely related to push notifications.

Whenever I receive a notification from Facebook, The Weather Channel Max or CNBC Real Time I get the icon. It is cleared after the app that sent it is opened.

Mystery solved but I still don't know if this is an iPhone "feature" or a byproduct of my jailbreak.