Why do you actually need this app if using Android? Wouldn't it be simple to just have a piece of paper with the required filters written down? Assuming what I see on youtube by experts is right, then one should always aim for ISO 100, fps 25 in the UK (maybe 30 in the US). Then it's just a case of using the app once (and once only), enter the various current shutter speeds to get the results and write then down on a very small piece of paper. As there is so little functionality in the Android app, nothing will ever need to be re-calculated as far as I see?
Current shutter speed (it only gives you a few in the dropdown list anyway): -
up to 1/100: no filter
1/100 -> 1/199: CP Polarizing filter (whatever that is)
1/200 -> 1/399: ND4
1/400 -> 1/799: ND8
1/800 -> 1/1599: ND16
1/1600 -> 1/3199: ND32
1/3200 upwards: ND64
In fact, looking at what I wrote above, it's even simpler. Up to to 200, no filter. Then up to 400, ND4, upto 800 ND8, upto 1600 ND16...... (see a pattern there)?
Am I missing something, or is it not just that simple; I can write that down and keep it in the bag with my drone.? Only thing I can see it is then useful for, is if you want to change the fps or ISO - as a novice, I probably never would.
Other comments are:
My Mavic Air can go up to 120fs (for slow motion), but the app only offers 24 or 30.
Shutter speeds to enter are quite limited. Having said that, I'm a novice and not got out of auto mode yet, so maybe in manual there are only those options anyway.