There are already plenty of attractive iPhone cases, purses, and holders that let you carry your phone around conveniently. The Cross-Body Clutch Strap is also worth a look. It combines with interchangeable clips to to hang from the back of your phone. It has a leather strap and holds your phone upside down for easy access.
These Cross-Body Clutch Straps work with Clutch Clips with industrial-strength adhesive. 2 sets of them are included but you can buy more to use them with all your favorite cases. This project is currently on Kickstarter. You can find out more about it here.