With the latest release of Nintex Mobile Apps (April 2015) barcode scanning is now available.
- To enable barcode scanning in your mobile form, you'll need to use the Single line of textbox control.
- In the Enable barcode scanning field, select Yes.
- Open your form in the Nintex Mobile App, and tap the barcode icon to activate the camera function.
You'll find the supported barcode formats here.
The blog post Nintex Mobile: Showing off it's Assets gives some more info.