Fun fact: Short of your DNA, your eyes' irises are your most unique feature, differentiating you from everybody else far better than your fingerprints can. EyeLock scanners examine 240 points in an iris (compared to 20 on a fingerprint).
Their technology has been used for security clearance applications for years, is now featured on a PC, and was being demonstrated in the visor of the Oak Ridge National Labs Cobra concept. At least one manufacturer is planning to incorporate EyeLock as an ignition lock, to identify frequent users and automatically tailor the user experience (seats, mirrors, infotainment preferences, etc.) to the user. Usage-based insurers like Progressive are also interested in knowing which family members are driving at what times. Lending your car to friends would be trickier, requiring authenticating their eyes to the car, but a valet mode with greatly reduced vehicle functionality, limited speed, etc. would negate the need to do that. The system can see through glasses and colored contacts, not counting spooky Halloween ones that obscure the iris.