I’d like to notify my users when something like a request failure occurs. However, I don’t want to interrupt the user by using a popup style alert. I’m looking for something like when you change the volume on the device and that translucent icon pops up and fades away after a second or two. During the time the icon is showing, the user can still interact with the app as if it weren’t there.
I looked in the HIG, but I couldn’t find any such UI control that is native to iOS. Are there any good open source controls that do this?

There’s an excellent control for a HUD-style popup called
SVStatusHUD. I belive it does exactly what you’re looking for: