It's difficult, because you cannot see the pixels in an HTML element's rendering with JavaScript. If you could copy a link to a canvas, then you could see if it has been previously visited, for example. So, canvases would not work.
1. Blur filter is only available on WebKit
2. I know for sure how much texture memory is on an iPhone 5
3. The touch event latency on android is too damn high.
I do synthetic scrolling (translate3d() + touch event interpretation and inertial math). Then duplicate the DOM for the top and bottom bars, adjust the positioning to make them look fluid and apply the CSS blur filter.
I may be possible with SVG filters or WebGL, but that also has security implications. It's possible to read cross-origin content using timing attacks and filters. http://www.contextis.com/files/Browser_Timing_Attacks.pdf