In the past couple of months I have read/heard about apps that can help me discover how well I am sleeping, monitor my heart rate, keep track of how many laps I run, how far I walk in a day...what else can they do? Do these apps require serious cpu power? or are they pretty light weight? I am thinking of buying a small, inexpensive cell phone and dedicating it specifically for the purpose of maintaining my health and fitness. What specs would I need on the phone? It seems that all of the heart rate monitoring sensors are bluetooth.