Nearly every modern point of sale self-swipe card terminal will allow you to swipe, insert pin, and sign electronically before the cashier can finish scanning your items. The only step left once that has completed is to approve the transaction total with the push of a button. I wish more people were aware of this, and then card transactions would be faster.
You can do everything up to that point - 'what type of card is this', etc... And many places are going signature-free below a certain transaction size, so I suppose all interactions can be handled in those cases before the 'total' key is hit.
Entering in/scanning your customer loyalty number and pulling out your credit card and scanning it (and pressing credit/debit) is what I've been able to "preload".
One other neat thing I've noticed is that at my Costco gas station, I can pull the pump out and select my gas type while simultaneously scanning my costco + credit card. I usually try to time myself with the person in front of/behind me to see if I can start my pump faster than them. I usually win :)