Hello, we can discuss more about what is your app exactly. I can also advice and help with the UI/UX perspectives for it. However we are 2 guys, I do all ui/ux and front end, and he does objective-c. Thus, i can guarantee you complete dedication and delivery, and covering all parts to make the final product as you require.
Signing NDA is not issue, or any other documents required. I am from Europe, GMT+1 timezone, available for communication, chat and more.
Thanks.