iSeaTracker is an app which turns your iPhone into a GPS tracker amazingly precise. It works with the isea3d.com services which let you display your track, with 3D graphics, and shared with your training partners or competitors. You access to the best debriefing tool for sailing activity. More information on isea3d.com
Continued use of GPS running in the background can dramatically decrease battery life. The use of the inboard battery or an external battery is recommended