iphone: what libraries or APIs need to be used for CPU , RAM usage in iPhone

I am pretty new to iphone development, can any body guide me 开发者_C百科through with some APIs and libraries which be used for:

1. RAM usage
2. CPU usage

in iPhone

need to do something like this app

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For Battery usage you can implement this notification

UIDeviceBatteryLevelDidChangeNotification 

I am not sure about CPU and Ram usage.