I will give my opinion.
It was nice that you tried to compile the frequently used features of a phone into an app, but these features are also available in the phone itself (pressing power button, volume keys. etc.)
What you could do though (as a suggestion) is to have a very useful widget that has all the features that you have in your app. It makes it more accessible especially even in the homescreen.
As i said...this is only an opinion and a suggestion.
Hope it helps in any way.