Letting website users know that there is an iOS app available - iphone

Question

In iOS6 there is an easy way to present users with the option to download your app when they visit your website and are on an iOS device.
(I know how to detect the user agent, write js, ect. Just looking to see if there is a quick nice library someone wrote for this.)
But, since that is not yet available, are there any good solutions out there to let our users know we have an app, and let them download it? But also, never show the message again if they HAVE downloaded it, or closed that dialog?
EDIT:
Here is what I have used in the past, but removed it because I felt it was annoying to the user. Just looking for lightweight examples.
/**
* Checks if this device is an iphone
*
* #version $Revision: 0.1
*/
puc.isIphone = function(){
return (
(navigator.platform.indexOf("iPhone") != -1) ||
(navigator.platform.indexOf("iPod") != -1)
);
}//end
/**
* Checks if this device is an ipad
*
* #version $Revision: 0.1
*/
puc.isIpad = function(){
return (navigator.platform.indexOf("iPad") != -1);
}//end
/**
* Function that checks if we are using a mobile browser and presents an option to view a differnt site
*
* #access public
*/
puc.mobile = function() {
if (puc.isIphone() || puc.isIpad()) {
// Add link to remove cookie
$('#copyright').append('<p><a id="remove-iphone-cookie">Reset Mobile Preferences</a></p>');
// Allow Deleting of the cookie
$('#remove-iphone-cookie').click(function() {
$.cookie('use_mobile', null);
alert('Preferences have been reset.');
return false;
});
if ($.cookie('use_mobile') == null) {
var conf = confirm('Would you like to download the PUC Mobile iOS app?');
if (conf) {
document.location = 'http://itunes.apple.com/us/app/puc/id424617272?mt=8&ls=1';
$.cookie('use_mobile', 'true');
} else {
// Never ask them again, unless they empty their cookies
$.cookie('use_mobile', 'false');
}
}//end
}//end if mobile
}//end mobile

Answer 1

The first part of your question is easy, you can detect the user-agent on the browser (serch for iPhone, iPod, iPad, etc... More here: http://p2p.wrox.com/content/articles/identifying-iphone-safari-user-agent)
The second part of your question is where you will come up short. You will not be able to determine that the user has the app installed because Apple will not share any user info outside its ecosystem (especially over the web). So you will need to show all users the info at least the first time. You could then set a cookie to track they have seen the info, but there is no guarantee how long that cookie hangs around.
Good Luck!

Answer 2

You could always just send a confirm alert with JavaScript once you have detected an iOS device such as the second example here (http://www.w3schools.com/js/js_popup.asp) but instead of 'you pressed ok' redirecting to AppStore URL and that will open in the AppStore automatically

Answer 3

Well, you can find out if an app is installed.
If the app listens to a custom url scheme you just try to open a url with it and if the browser is still on the page ofter a set timeout it is not installed. This is you implement links that either open the app or the app store.
And that's tricky since you can't cancel if the app is indeed installed, the link will always open your app.