Firebug for iPhone
A little Python web server which acts as a bridge between your iPhone and the Firebug console running in the browser on your computer. When you call console.log() on the phone it sends your log message to the server, which reflects it back to Firefox (or Safari or whatever), which displays it in your nice big Firebug console. You can also enter JavaScript commands in the command line in Firefox and have them sent to the phone, evaluated, and sent back to Firefox. It all works surprisingly well!
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