I noticed UnifiedPush and your efforts there and I am curious. My summary after a brief glance is UnifiedPush will not achieve anything useful, for the same reasons: iOS and Android push notifications are locked down. For example, sure, Android is OSS, but most of the functionality is provided by proprietary apps or Google Play Services. This results is challenges today, but further challenges down the road (App Store rules/policies change, stronger enforcement).
About the battery usage, this is always a hard question to answer. 4% is very low, which seems good. But how could you measure that effectively? Perhaps if the connection is good, it might take 4% battery over 17h of "use". But could this be worse if network is intermittent (i.e. realistic conditions)? Or lots of data being used (or *abused*).