Augmented Reality is the killer app for the iPhone 3GS
blog.bumblebeelabs.com
blog.bumblebeelabs.com
That's a video of what Augmented Reality can do on the G1... definitely cool app.
Thus we will soon have 3d goggles, sensors for anything, chip implants, body hacking, brain-computer interface and the kitchen sink on the iPhone =)
What's needed is an interface that can convey information but which is not a soak for all of your attention. A 5x8" form factor which is extremely lightweight and daylight readable could be held like a cue-card. Add accelerometer, compass, camera, good contextual voice recognition, and GUI which is easily operated by one thumb, and you have it.
Heads-up displays on your contacts, or direct neural inputs would be dandy. I think we'll get the above before that, though.
http://www.sparkfun.com/commerce/product_info.php?products_i...
Anyone who's read a Charles Stross novel in the past 2 years could see this one coming from a km away.