a button where you can add with one click packagelists to you system (for example: "add this PPA to your system")

I would like you to think about this very useful feature:

If I would add a packagelist which is posted on a website, I would find it very useful, if there´s a button, which looks for example like „add to system“. If I click on it, it should add the packagelist, and also the signing key. It´s essential, that this could only work after typing your password in.
I don´t know how to realise this feature, but I find it good, if you think about it.
thx