I would love the idea of keyless entry, but that's not about to happen anytime soon, sadly.

The ideal implementation would be like Apple's SUICA integration in Japan: built into the operating system and designed to work without any interaction with the device, just a tap, and with a special power reserve so that it continues working even when the phone is dead. It's absolutely incredible how good the experience is when it's implemented right.

It would require cooperation with Apple, but it could be done, and it could be an incredible co-branding partnership for both companies.