Interesting idea, could be very useful. One thing with this kind of service is always how they handle validation of data from the 3rd party service (eg, in headers). So as an example http://hurl.it/hurls/db870b49c7203ec9acb47ba7769c126146b1768... executes javascript in the context of their site... (just a pop-up box with hi, but could be any script..)