The Xiaomi Yi 4k Action camera was one of the biggest breakthroughs in quality over price when it came to action camera clones. It is literally a direct GoPro Hero 4,5 and Sony Action Cam rival with very close specs and performance but with a price tag of $199 it really is in a category all by itself.
The current Yi 4k camera is no slouch in the specs department but recently leaked information shows that the Yi 4k+ will have at least twice the processing power for 4k video and some hint at even faster frame rates.