Came here to say exactly this. It just uses the battery charge up so quickly when I am out in the garden and triggering alerts/recordings every minute.

As an alternative to identifying when a user is on the LAN, you could build in geofencing to the app. So if I am outside a 200m radius of my house then activate PIR, otherwise disable it. This could then be used with other users sharing the camera (e.g. a wife), so PIR is only active when BOTH users are outside 200m. This kind of functionality really makes the camera/app "smart".