It's called Image Sync, and you'll find reference to it in the PDF owner's manual. It's about as medium wonky as virtually all such WiFi apps, but it gets the job done. At least it's in-camera!
Even though my K-3 is arguably superior on almost every essential way, I find that the K-S2 is what I always grab when I leave home- it's just a really, really fun camera to use, and so small that I can pack a serious kit into a very small and light camera bag. It's a good idea to acquire a spare battery or two for your kit, BTW.
Also, check out Pentax Forums for all the answers to anything Pentax related.