Laser-accelerated ion beams have very special properties because of the unique acceleration process. They are created in ultra-short bunches of high intensity with typically more than 109 particles/cm2/ns, making online characterization of these beams an ambitious task. As first step towards an online beam monitor for laser accelerated protons, a pixel detector based system has been integrated into a spectrometer as position-sensitive element in the dispersive spectrometer plane. The pixel detector system is based on a commercial detector, the RadEyeTM 1, a large area (2.5 x 5.0 cm²) CMOS image sensor. The sensor array is arranged in a matrix of 512 x 1024 pixels with 48 µm pixel pitch. In the present configuration up to 4 sensor modules can be read-out in parallel, thus allowing the coverage of a sensitive area as large as 50 cm2. The detector system has been thoroughly characterized at the Munich 14 MV Tandem accelerator in an 8-20 MeV proton beam in dc and pulsed irradiation mode, the latter simulating laser-accelerated like ns ion pulses. The detector system is able to resolve individual particles of the beam and saturates at a maximum pulse intensity of 107 protons/cm2 (20 MeV), showing a linear response over the whole dynamic range. Cross calibration with CR39 nuclear track detector and using laser-accelerated protons from the MPQ ATLAS laser, showed good agreement with the Tandem calibrations. A compact detector setup with integrated read-out electronics and on-board PC is now in routine use in laser-acceleration experiments. Ion spectra can be visualized in real-time on a shot-to-shot base, a major step with respect to beam monitoring in future applications of laser-accelerated ion beams. This work is carried out in the frame of the DFG funded cluster of excellence Munich Centre for Advanced Photonics (MAP).