Sparkle for Web apps?

For anyone who has used a Mac app with Sparkle in it (Colloquy, Adium to name a couple) knows what a breeze they are to update.

While I appreciate Mint helpfully tells me when there is an update, I wonder if it could do more. Sparkle is actually a rather simple thing. It:

1. Checks for a new version,
2. downloads it to a temporary space,
3. closes the app copies in the new files/binaries,
4. restarts the app,
5. and deletes the temporary files,
6. Fin.

I wonder if with the magic of Curl/Wget etc this would be possible for a web app to do. It could shut itself down using an .htaccess with temporary redirects to send everything to a holding page. Then update itself by copying the new files in and remove change the .htaccess back to the regular state to allow access again.

This may become yet another side project to make a PHP version of Sparkle.

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Web Development, sparkle, autoupdate