I normally don't cover apps too early before they're released but I couldn't wait to post about Promotee. It will shortly be going into Apple review, so expect to see it in about a month.
From the fine folks at Netwalk, Promotee lets you drop pictures into framed tableaus, enabling you to build promo images from your app's screen shots.
It's tremendously easy to use, and developer Tom Nys tells me they'll be expanding the art over time. The app currently supports most recent iOS devices, Macs and several Nexus models.
They plan to launch at US$4.99. For your fiver, you'll get a tool that creates simple, elegant product art in seconds. You can find out more about the app and its launch status by pinging Netwalk by email or leave your email in the "stay informed" section of the Promotee page.