I got a spare for $115 at BB, read my headache above.  Someone said there are aftermarket batteries out there, no WAY would I try that, the whole grand worth is depending on that battery readout being accurate and not freefalling from the sky.  I use my iphone 6+, because it's light and not all bulky.  At times a bigger screen would be handy, but I don't feel like downloading maps and all and I am not paying a monthly fee on my tablet just for that.  I have an android tablet that is strictly used as a planter monitor display that I could use, but once again, I don't have a plan on it and not going to.  I don't suppose there's any reason you have to though.  You don't really need a lot of device storage, I delete most of my copied footage on my phone anyway, as the card in the copter has it all in 4k anyway.  Very seldom do I fly that I don't get a lower res signal on my screen of lose it altogether so the phone file is pretty much junk anyway.