The InstaCorr menu on the Define Overlay control panel has a new entry: 3dTstat.
This menu item will let you interactively run 3dTstat to compute a voxelwise statistic from a time series dataset. There are 43 statistics available.
One new such statistics is MSSD = Mean Square Successive Differences = a measurement of how much the dataset fluctuates between neighboring time points. Related to that is MSSDsqrt, which is just the square root of MSSD, and MASDx, which is the Median Absolute value of Successive Differences (multiplied by 1.4826 to make it comparable to MSSDsqrt).
These changes are in the source code (on github) now, and should be compiled into AFNI binaries over this weekend.