Love the website and the simple but effective design.
Here are some things that bothered me:
This looks like a mistake, the text ends suddenly, try to fix this by adding some padding at the bottom to establish a 'smooth' ending.
I would make the lines for outline of the iPhone more consistent in color and size. Notice where the yellow outline box the color and line size is not the same as the exterior outline as well as home button outline? From a visual perspective this piece does not look like it is appropriate to the rest of the model.
One more tip. it looks like you have a .gif or video playing on the iPhone, I would recommend a new video/image. Why? because it lags like crazy and its hard to visualize an effective workflow for the user. If you are going to demonstrate user workflow of your product you should show the best of the best user experience. By lagging in this image I automatically make the assumption that it will lag as an application on my iPhone.
Hope these tips were able to help you out.