Photoshop Touch will still set you back $5, no matter which platform you pick. And yes, you'll have to buy it again for your iPhone, even if you have it for your iPad already. But, the experience is extremely similar. You get layers and selections tools, and filters, and adjustments as you'd expect. But, they've also added something called Camera Fill, which lets you fill in a selected area with a photo taken on your phone's camera. It's kind of like making a double exposure with a real-time preview.