If all our devices accepted swipe cards they'd be probably more useful than fingerprint readers - with the added bonus you could have different ones for different types of sites. (Business, personal, etc.) Visit site - it asks you to swipe your card - you do and you're in. With pin-numbers required for only the more important sites.

Or could an equivalent system be created for USB ports or whatever's the most common? ie. Some kind of dongle you'd carry around that says to sites that you are you. No physical logging in at all then, it happening automatically as long as your dongle's plugged in.