Seeing the post on the front page about Useless gauges made me think about a gauge that I always wish cars were equipped with - altimeters. Considering that most cars nowadays are equipped with a GPS sensor anyways, it would be simple to just pull the altitude data and display it on a digital gauge someplace. This would be less accurate than a true altimeter but is an easy way to accomplish this within a useful ballpark for driving purposes. I would love an incredibly accurate barometric pressure based altimeter along with a nice analog gauge but I am weird like that. It would just be really cool to drive over some mountains and know what altitude I am at without having to google it or rely on the highway roadsigns that indicate the altitude in some places.
Now this might be irrelevant for someone in Iowa living on a prarie that doesnt change in elevation for miles. But here in California I am going up and down in elevation all the time. I know I change at least 1000 feet over the course of my commute to work and the temperature changes on my temp gauge for outside really show this.