One Killer Feature I'd Like to See in the Next iPhone...

Really great, well implemented NFC integration would be killer.

Apple could reinvent the credit card.  Apple could partner with all of the top credit card companies (in typical iTunes-fashion) to provide for an easy to use, intuitive and intelligent payment solution.  It would have system-level integration with iOS.  You could ask Siri to check your current balance, make a payment, contact the company/person who you are exchanging and making payments with, and even to remind you of certain payments that are due or need to be executed.

Push notifications will allow for you to keep track of your money and payments.  Direct integration with Shipping Carriers such as UPS an FedEx will allow for easy tracking on your shipments and pickups.

Touch your iPhone to an NFC reader at a store and confirm the payment.  You will then have an accessible record, at anytime with all of your receipts.  This is synced with iCloud to show up on all your iOS devices, seamlessly and automatically.  It just works.

It will open up a world of sharing possibilities as well.  Touch your iPhone to a friend’s iPhone to share contacts, application recommendations, and more!  Even make payments, securely, between you and your friends/clients.  This makes business incredibly easy and intuitive.

There can even be tight social integration (optional) with services like Twitter to allow iOS users to share recent purchases, online or in the real world.  Friends can share their purchases with you, and you’ll be able to see an entire world of deals and opportunities.

Overall, this could be a revolution of the incredibly outdated paper money system we currently use, here in the US.  To be able to make payments easily, take care of business, share with your friends, and even be reminded of payments makes keeping track of expenses so easy.  It just works.