In the past I have used Median Absolute Deviation to test for outliers in a static series of data. This is a simple measure to implement and is related to standard deviation for normally distributed data points. I have used it for a static data set rather than a time series but it should still be efficient. 

The median absolute deviation is defined as the median of deviations from the median 

![enter image description here][1]

and you can find out more about it here http://en.wikipedia.org/wiki/Median_absolute_deviation


  [1]: https://i.sstatic.net/Zh7TH.png