Thanks Danny D,
I see there is no lack of slow-mo players. Looks like I've found a niche on the market, anybody ????!!!!
My $30 Aukey dash camera doing exactly the same what I need, and even has mini HDMI out. I will think if I can hook it up with any 7-10" display or laptop. But none on Android or iOS market, it's a big surprise, I thought that in modern world everything already exists.-)
I think this is because Camera app on mobile is very complex and require some proprietary legal stuff, so all slow-mo apps I tried use native camera app for actual recording, then you need to <load video> for play or edit.
Best
Dai