I’ve used UIWebViews on top of an app with an openFrameworks core, basically by extending the iPhoneGuiExample view. You can easily add a webview to that example, and then talk to it.
I added a transparent background webview with code, but you can also use the interface builder.
in your .h
UIWebView * myWebView;
in your .cpp
-(void)viewDidLoad {
myApp = (testApp*)ofGetAppPtr();
myWebView = [[UIWebView alloc] initWithFrame:CGRectMake(0,0,320,323)]; //x,y,w,h
myWebView.tag = 0; // for reference purposes
myWebView.backgroundColor = [UIColor clearColor];
myWebView.opaque = false;
myWebView.delegate = self; // this refers to the GuiExample view. Because of this you can put functions like webViewDidFinishLoad to the GuiExample and the webView will know where to look for it.
myWebView.scalesPageToFit = YES;
//also handy: I didn't want the directional lock, this is the trick to do that
for (id subview in myWebView.subviews)
{
if ([[subview class] isSubclassOfClass: [UIScrollView class]]){
((UIScrollView *)subview).bounces = YES;
((UIScrollView *)subview).directionalLockEnabled = NO;
}
}
[self.view addSubview:myWebView]; // this adds the webview to the GuiExample
}
Then for instance if you want to show a complete HTML string with local images you need to make sure the baseURL refers to the location of the App on your device:
-(void)loadHtmlStuff: (NSString *)myHtmlString{
NSString *path = [[NSBundle mainBundle] bundlePath];
NSURL *baseURL = [NSURL fileURLWithPath:path];
[myWebView loadHTMLString:myHtmlString baseURL:baseURL];
}
UIWebViews, like any other view, comes with a lot of great built-in functionality, in this case for instance the -webViewDidFinishLoad function. Add this to GuiExample:
-(void)webViewDidFinishLoad:(UIWebView *)webView{
switch ([webView tag]){
case 0: //the reference tag we gave myWebView
[self hideMyView:false]; //some function in GuiExample that only shows the webview when completely loaded
myApp->myWebViewLoadCompleted(); // call oF function to handle the rest
break;
}
}
You can also call a javascript function that you’ve put with HTML inside UIWebView to set / check for things. It’s really handy! 
NSString *myJSFunction = [NSString stringWithFormat:@"javascriptFunction(%d,%d);", firstInt, secondInt];
[myWebView stringByEvaluatingJavaScriptFromString: myJSFunction];