The effectiveness of these all depend on your SNR.
How about a simple moving average (SMA) on the absolute value of the data and look for the result to be below some threshold? The size of the SMA window would depend on the noisiness of the data. That uses a for loop, unfortunately.
A slight variation would be to traverse the data array and check for the last N elements all below a threshold. Again, this uses a for loop.
Or a combination of my original idea and ShaunR's... Do the diff (or sum) with the array shift, compare to a thresh, then convert from boolean to 0,1.