I hope you plan to implement a notification system in JUCE, so I want to help you by pointing at the right direction )))
Have a look at the libevent library located here http://www.monkey.org/~provos/libevent/
The last version is 2.0.7 (I don’t recommend you to use any lower versions since they are considered to be much slower)
It’s being distributed under the BSD licence so you can use it in JUCE with no worry.
It supports multiple operating systems, but I’m not sure about iOS that’s used on iPhone.
I hope it’ll be useful for you )
P.S. Oh! Alternatively you may take a look at another notification library called libev that’s claimed to has a somewhat higher performance than libevent. You can find it here http://software.schmorp.de/pkg/libev.html