I'll definitely keep an on the tires and mileage. I don't remember the brand that was on there originally, but they never seemed to grip well.
Would we be more efficient without gadgets? I'm sure we would, but at what cost. I don't think that most of the gadgets, the nav system, the CD players, etc. add a lot of weight to the car. You're talking a few pounds. Leaving a laptop in the car when you don't need it probably adds that weight. Also, most cars recharge their batteries with an alternator as we drive, so without the gadgets, some of that power would be wasted.
Hybrids have 2 batteries. One is for normal gadgets, and that's a 12v we're used to. The other is larger and used for moving the car
If we removed safety gadgets, things would weigh less, but what do you want to remove. I think we have perhaps gone overboard, but what do you give up. Seat belts? front air bags? Side air bags? Less steel and more air bags? Not sure here.