I don’t have the iOS app yet but I have used the device tracking in SmartThings and several other platforms and was disappointed to find it just destroyed my battery life. Is the device tracking in this app designed any differently and how is it affecting your battery life?
I am currently using the App Locative in combination with iBeacons and there is no noticeable difference in the battry life. I hope the iBeacon support is on the shedule of the iOS app! 
I’m using owntracks(on my Samsung S5) and pulling the location every 5 mins for better accuracy. At the end of the day, the app uses ~5% of my battery.
It really shouldn’t affect your battery life much if at all as it uses significant location updates as well as enter/exit of geofences which are created around any zones you have defined in your Home Assistant configuration.