What's the best measure of how much a value changes? From a car, I get a value every second for accelerator pedal, from 0 to 100%. When you don't touch it, it reports 0%, and when you kick it to the max, that is 100%.
I want to calculate how much change there is in this value. It will be one of many  indicators of how you drive (how aggressively). 
The best I have so far, is to calculate the average absolute value of the change from one reading to the next. 
I am sure statistics offer something better, but I don't know what. 
My reasoning is that variance is not relevant. What I want is more like the total work you do on the pedal divided by how long the trip is. 

When posting this, I have to specify tags. When writing "change", autofill suggest "change scores". Is that something I should look into?
 A: Average absolute value from one reading to the next is potentially a very good measure of volatility.  You might consider whether a 1 second interval is optimal, vs. computing successive changes after averaging over, say, 3s intervals.  Other useful summaries might include the maximum acceleration over a long time period, and the 0.9 quantile of the 0-100 acceleration measurements.  But it would be nice to have data on break usage, depending on what your real unstated goal is.
A: There are two analogous areas in which you may be able to find pre-existing formulae. 
Water level measurements over time: it seems you are truly seeking a measurement similar to the most common water level over a given time period. Farming and geological sites will have loads of equations related to that for you to convert easily. 
The second one is network bandwidth billing. A common billing measure is to take the 90th %ile of of average usage as the billable amount. This allows for the exclusion of brief spikes throughout a given time period. 
Asking the web about water levels over time, or bandwidth utilization measurements should yield you a lot of substantial results. 
