SWAP (Sun Watcher using Active Pixel system detector and image processing) is a solar imager in the extreme ultraviolet (EUV) that has been selected to fly in 2007 on the PROBA 2 technological platform, an ESA program. SWAP will use an off-axis Ritchey Chrétien telescope equipped with an EUV enhanced active pixel sensor detector (coated APS). This type of detector has advantages that promise to be very profitable for solar EUV imaging. SWAP will provide solar coronal images at a 1-min cadence in a bandpass centered on 17.5 nm. Observations with this specific wavelength allow detecting phenomena, such as solar flares or EIT-waves, associated with the early phase of coronal mass ejections. Image processing software will be developed that automatically detects these phenomena and sends out space weather warnings. Together with its sister instrument LYRA, also onboard PROBA 2, SWAP will serve as a high performance solar monitoring tool to be used in operational space weather forecasting. The SWAP data will complement the solar observations provided by instruments like SOHO-EIT, and STEREO-SECCHI.