Chip-size wavelength detectors are composed from a linear variable band-pass filter and a photodetector array. The filter converts the incident spectral distribution into a spatial distribution that is recorded by the detector array. This concept enables very compact and rugged spectrometers due to the monolithic integration of all functional components on a single chip. This type of spectrometer reveals its most convincing advantages through appropriate systems integration. We discuss the advantages of this concept for spectroscopy of light distributions that are hard to focus onto the entrance slit of a conventional spectrometer, namely large light emitting areas and moving point-like light sources. The excellent spectral performance of the system is demonstrated for both light input geometries.