You don't need a frame redirect.
(1) Set up a subdomain called "www", and have your naked domain (mydomain.com) redirect to www.mydomain.com as an http redirect.
(2) Sign up for "Google Apps for Business" using "mydomain.com" as your domain.
(3) In the Google Apps dashboard, find "App Engine Apps", and add your app-id.
(4) Click on your app-id and From there you can add additional web addresses for your app. Add "www.mydomain.com" here.
(5) In 1&1 you'll have to update your www.mydomain.com DNS settings as CNAME, with alias "ghs.googlehosted.com"
With all that done, mydomain.com will http redirect to www.mydomain.com, which in turn will alias to ghs.googlehosted.com, which in turn will pull up your app.
You can then cleanly use your domain URIs, ex: "mydomain.com/getPineappleStatus?id=12"