There's a pretty big market for this/enterprise level identity management in general. At least in Germany, companies usually prefer inhous/more control over hos

There's a pretty big market for this/enterprise level identity management in general. At least in Germany, companies usually prefer inhous/more control over hosted solutions though (especially in the light of the last 1+ year). SAP IdM is the big dog here (it's somewhat messy though since SAP bought the technology and it shows that it's somewhat of a hodgepodge imo) and the only one I've worked with. I'm sure all the big ERP companies provide this in some way. Not really the API you're looking for but I thought it was worth mentioning.