I came up with this a couple years ago. I have a Flex Case made by BodyGlove for my iPhone 4S, which has a removable **** on the back for attaching to a belt clip. I took the **** out, leaving a hole in the back of the phone case, and put the **** on the dash. I can now hang my phone on it like a hook.

I love that I can take the phone on and off easily without having to engage/disengage a connector... the cable just stays attached. The only downside is the adhesive left behind on the panel, but that panel can easily be replaced for a few dollars and a little work.





Unfortunately, they aren't making this case for the iPhone 5/5S...

 

Here's another pic of the final result.