Silver looks pretty impressive.
Silver is the first prototyping tool built exclusively for Sketch. It is perfect for making quick, flow-based prototypes, but it also plays nice with Framer.js to help you add micro-interactions to your Flows.
Makeing prototype connections directly in Sketch. Seems to be a dream come true. Let's just hope their product will be able to keep the promises.
More about the why he created it: Introducing Silver
I would love to try it today! :)