Global Login (kinda like .NET Passport)

ok so i have decided that i want all my sites to run on one user database, ok peice of cake. i have coded mine in PHP. It just remotly connects to the database and fetchs the userinfo and some special info about the site and feilds relative to that site. However i have yet to decide if i want to update this to work on a XML format. The only way i would bother to upgrade it to that is if people would be willing to buy it. So the question is, would anyone be interested in it (not saying that it is for sale, or a price)?

im going to get a feature list up here soon