Besides the basic text-editing, cloud-sync, and ebook publishing tools you'd expect in a platform like this, there's also a big linguistic model of literary prose, which helps authors analyze the vividness of their writing, and make meaningful comparisons against the authors they admire.
Anyone online can explore the public version of that model, at http://prosecraft.io, but subscribers of Shaxpir can actually analyze their own writing according to the exact same model, getting realtime feedback on the linguistic metrics of their prose.
I launched my beta about 3 years ago, and this is the 3rd time I've applied to YC... I applied to the original Fellowship, in the fall of 2015, and then to Winter 2016 class.
Fingers crossed!
And best of luck to everyone else who applied!!
But even if you don't get accepted this time around, just KEEP WORKING! Eventually, you'll find a way!