Running answers right away is fairly useful; a bit of a challenge in that problem domain is with multichannel sensors ("cameras" with multiple frequency bands, satellites like MODIS, radiometric spectrometers, etc.) where the sharpest "image" is produced by using an SVD (singular value decomposition) type transform to reduce (say) 256 input channels to (say) 6 major dimensions and using those to recreate an enhanced image. Producing branchless code to generate basic running stats (min, mean, max, variance, trends) on multiple input channels is a bit of puzzle, generating an efficient rolling SVD enhancement (best image based on most recent observations) is a bit trickier.

The application areas are continuous processing of continuously arriving data, infinite unbounded sequences.