Fprintd is a D-Bus daemon that offers libfprint functionality over the D-Bus interprocess communication bus. By adding this daemon layer above libfprint, we solve various problems related to multiple applications simultaneously competing for fingerprint readers. While it is not very nice to think of a daemon being necessary in this scenario, fprintd will be launched by D-Bus through the activation mechanism. This means it is launched only when needed, and additionally it will shut itself down after a period of inactivity. (Text copied from link below.)