Question: I have found that certain android applications show my site, I think they use with webview, 
How do I block all applications that can show my site ?

Answer: 
> 
> How do I block all applications that can show my site ?
> 
> 
> 

You have no means of conclusively determining what software is sending the HTTP request, and Web browsers are "applications". So, either take down your site, which will "block all applications that can show [your] site", or do not worry about what "applications" the user has chosen to view your site.
I don't think there is a 100% secure way of doing this. What you can do is to attach a header property to your app browser with a server-validated key. Without this key, in combination with a [mobile browser detection library](http://wurfl.sourceforge.net/php_index.php) you'll know if the app is authorized or not.

But if a developer acquire this key there is no prevention for him to implement it. Also detecting a mobile browser is not an exact science.