Sorry, I would just test this myself, but I'm currently without my mac. Does a web request made inside of a UIWebView send the same user-agent info that a web request made from mobile Safari would?
Web requests made from UIWebView will not include the word "Safari" in the User Agent string. Web requests made from Mobile Safari will. This is the best way I have found for determining of a request is coming from within an app or from Mobile Safari.
Sample User Agent from UIWebView within App:
User-Agent: Mozilla/5.0 (iPad; U; CPU OS 4_3_2 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Mobile
Sample User Agent from Mobile Safari:
User-Agent: Mozilla/5.0 (iPad; U; CPU OS 4_3_2 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8H7 Safari