I tried to make some slow motion footage with the Osmo Mobile (v1) + DJI Go + iPhone SE but could not select the framerate / resolution just like the iPhone does.
Am I missing a setting, or is that not (yet) implemented?
PS, now the footage turned out as 720p footage.

I am pretty sure that you need an iPhone 8 or X to record 240p slo-mo at greater than 720p resolution. Some models may allow 120fps @ 1080p but limit to 720p when shooting 240fps slo-mo.
At least that's my recollection. I no longer have any older devices to test it on.

jrm11 Posted at 2018-5-6 09:35
I am pretty sure that you need an iPhone 8 or X to record 240p slo-mo at greater than 720p resolution. Some models may allow 120fps @ 1080p but limit to 720p when shooting 240fps slo-mo.
At least that's my recollection. I no longer have any older devices to test it on.

That is true, but the 120 fps could be there.