"see's" hazards ahead and alerts the user with a loud siren. I believe you can set its sensitivity. That being said I never use it because I'm loath to keep looking at a phone in the cockpit and it consumes the battery, as well as the phone not being waterproof. Its a terrific piece of software however and if its available on a smart phone how long will it be before the chartplotters have it too? I don't know, my idea about a simple expanding square built into chartplotters from the time a COB button was pushed connected to the autopilot was never picked up although I wrote to CE and I think Raymarine. Practical Sailor published it, in a letter to the Editor.