Merd !!! I don't think the e-tube downgrade works on an ipad or iphone. Most people resort to buying the cheapest possible android phone/tablet to get around that ..
iOS App for Shimano motors is available - EMTB Forums
I know you did say "app store" at the start, but in my mind I didn't differentiate the difference... doh.
However, vadll does say it's possible with iOS in December :
iOS App for Shimano motors is available - EMTB Forums
But the thread dries up on how to do it (like where to copy the files etc)

So not sure if that's accurate or if vadll just had a moment and didn't notice the ios part of the question....
OK .. we're working on the fly here ... raine says he did it with his iphone in october ..
iOS App for Shimano motors is available - EMTB Forums
Just reading back now and the link I gave you to the emax pdf and the one from Raine both link to techniques which require the PCE/windows interface - so that wasn't very helpful was it !
This sucks doesn't it ...
I can't actually find anywhere with step by step instructions on how to downgrade the firmware using eTube on iOS. It looks like you could download the files from emax, but I'm not sure if they're the right ones as they appear to be the ones for use with Windows.
@raine .. He's not wrong, this isn't actually conveniently documented anywhere. Or at least not anywhere either of us can find it. In the interest of anyone who wants to do it, is it worth you two doing kissy kissy make up, or at least agree to be frustrated with each other like a married couple and making a new thread "How to downgrade E8000 firmware using IOS - for Muppets" .. Yes, I'll let you use my copywrited muppet tag ..
Rocking in on the left with 245 Posts .. we have Polaris .. On the right we have Raine .. with 244 posts .. ding ding .. round 1.
I'd do it myself, but I don't have an e8000 bike anymore and the only iPad I have is in the first aid kit. There are some apples in the kitchen, but throwing them at the Kenevo isn't going to come up with the solutions anyone needs.