Integrity checks the links and images on your site. Feed Integrity your homepage URL and it will follow internal links to find all of your pages, checking each link and reporting the server response code for each.
On features - I intend Integrity to remain a free website link checker, no more no less. Note that Integrity Plus offers more features such as managing multiple sites, exporting and sitemap generation. Scrutiny provides further advanced features such as authentication, spelling and grammar checking, and SEO checks.