Hey,
Thanks for the code!
First of all I'm new to react-native.
I'm trying to develop something like this: http://jsfiddle.net/soundar24/LpuLe9tr/3/
And your code seems the closest react-native I could work with.
I've imported CircularSlider, put the <CircularSlider> part and now I'm getting this error:

Line 49:
d={`M${startCoord.x} ${startCoord.y} A ${r} ${r} 0 ${value>180?1:0} 1 ${endCoord.x} ${endCoord.y}`}
I replaced it with another value d="M10 10" and it showed something correctly, that's how I concluded the error line.