Hi Sue,
I'm just finalising my own lists for August. I previously lived in the Centre and have done most of the Larapinta, just not all at once.
I'll be using Micropur tablets for water purification, if we need to use ground water which looks a bit dodgy we will boil and/or use a filter cloth. Quality and availability of ground water will depend on rainfall between now and then. You should NOT rely on ground water (waterholes, rock pools etc.)
Your phone may go flat quickly if you leave it switched on, as there will be no service. I saw from walkingwithwild's blog, that there are a few high points on the range where 3G is available, I would assume only with Telstra. Otherwise once you are past Simpson's Gap or thereabouts I wouldn't expect any coverage.
I will be putting spare batteries in my food drops. As for the camera... gee I wish I'd bought more of those cheap camera batteries in Nepal!! I need to suss out what charging facilities are available, but I can see it being a bunfight over power outlets, if and where they are available, and I'd prefer to avoid that. I have a small power pack that I'll put in - otherwise I will simply be conserving batteries between camera & phone. Having a local co-walker and other friends, means vehicle support for us in a few places, which is mighty handy.
What is necessary... a flynet can be a lifesaver, again depending on the season. My mate in Alice tells me today that it has turned cold - but if there aren't any savage frosts before your planned dates, the flies can be bad in a couple of spots. Section 3 springs to mind.
Depending on your itinerary you'll also need some capacity to carry enough water for 2 days in a couple of places.
And a love of red dirt doesn't go astray
