Srtm2Osm tool uses Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) to generate elevation contours (isohypses) of a selected terrain. The tool writes contours as OSM ways into an OSM file. This then enables rendering of the terrain using Osmarender XSLT transformations or other OSM renderers.
See this issue on the OSM-Wiki talk page.