Which device uses "Mobile Safari UIWebView" as the browser name? In looking at the browser name from our internal web stats I see "Mobile Safari UIWebView".  

What device does that represent?  

We record "mobile safari" separately (and is used 5 or 6 times more).
It is not a specific device. It means that your web site was viewed using the UIWebView functionality on an iOS device (iPhone, iPad, iPod Touch). 

The UIWebView is different from the ordinary Safari browser, as it is not a stand-alone browser, but merely browser functionality that is embedded in a third party app.