Ok, I want to make a speedometer for my car using the Arduino and an accelerometer... It'll basically just get acceleration and then use a physics formula (can't recall it now >.<) to determine speed (since I know time between last reading, initial velocity and acceleration, is it Vf = Vi + a*t?) And I want to store 1 value every second, the value will be in a two dimensional array like this:

values[#][0] = velocity (int)

values[#][1] = acceleration (int)

values[#][2] = number (int) (this is the number of readings taken since the device got power, since after a certain number, it will overwrite the array, then I can just order it by this dimension instead of bumping the array down with each new reading)

So that's a two digit number, a 2 digit number (maybe doubles for these actually), and another number ranging from 1 digit to 4ish, I want 1 second intervals for 30 minutes before it begins to overwrite, which would be 1800 two-dimensional arrays... I know this won't fit on the chip (will it) so I was going to get some external flash, but I'm not sure how much. Thanks