google analytics with out the new google analytics (the old google analytics interface using the google analytics API) .. as soon as google sunsets the old version (what they wanted to do last jan) there will be a lot frustration (as the new GA - currently - sucks, hard)
huge market (there will be millions and millions of frustrated users) - can easily be a premium market (5$ to 25% per user?) - i would be the first to sign up.