Let us imagine for a moment that I have a piece of hardware that can act as an authentication for a user on a given system. I want to write an application in C++ to run as a service, look for this device and if found log the appropriate user in. I believe I have found the API's I would need to use to perform the hardware and service portions of the application but am having a hard time nailing down a way to create a "real" user login. Is this possible? If so where would I look to find resources on accomplishing this? I think of it as being an analog to fingerprint scanner login type devices.
I think you are probably looking for the GINA ("Graphical Identification aNd Authentication) APIs. There is a good tutorial here.