MockUp

While most apps are limited to only building UI or interface prototypes, MockUp is your all-in-one app to do that and more.

With MockUp, you can:

Build UI prototypes
Create storyboard mock ups
Trace images for best and most versatile prototypes
Create printable and editable prototypes
Can import images to trace

You can export prototypes/transparencies as PNG images that can be imported into any program. Many apps were built specifically for Balsamiq or Photoshop - which isn't very useful if you don't have big bucks to buy them. If you don't have either of those, you lose out on the greater majority of the functionality and versatility. By simply exporting PNG files to an email address, printer, Google Drive and other services allows you to be platform independent and to share your prototypes and ideas easily.

Free drawing tools allow for the ultimate customization of prototypes. Other apps are restricted to JUST interface mockups. Free drawing will let you create what you want. Tracing over an image gives you free range to prototype anything you can take a picture of.

This app is perfect for drawing out an idea as well as creating a simple prototype to pitch your idea.