Does this work on iPads, iPhone, tablets, Androids, ...?
It should, sadly it doesn't. Google offers a tablet/mobile experience for some mobile/tablet devices. This experience sadly redirects users from the "Google Search by Image" search page to the Google homepage. The bug is already reported to Google. You can star it to make it more prominent.
Does this work with Internet Explorer 6/7/8/9/10/...?
I did. Well kinda. I glued it together. The "Search by Image" functionality is provided by Google. Accessible via a simple URL. The canvas drawing thingie is a fork of drawingCanvas by a guy called balaclark. The Flash webcam thingie was created by taboca.
How does this work?
You mean technically? Quite simple actually.
You draw something on an HTML5 canvas.
Click on Search
Image gets converted into a base64 encoded data uri
Image data gets send to server (powered by Heroku)
Image gets uploaded to Amazon S3
The Amazon S3 Image URL gets communicated back to your browser.
Browser gets redirected to Google Search by Image.