... it was hidden by the genoa. The worst part was I knew it was there but didn't peer around the blind spot from the genoa frequently enough (lost track of time and didn't think we were near yet). The damage was minor but I considered it a wake-up call. One of those stupid accidents one kicks yourself over. "How could I be so STUPID?".

After that I was looking for a suitable timer and found the Watch Commander device. I was watching eBay for over a year, never found one used.

Meanwhile -- I bought one of these Invisible Clock II units a few years ago and it works quite well. It doesn't have the feature of getting more annoying if you ignore it, but I can clip it to my waist or PFD strap like a pager and it will beep at whatever interval I set. When we are day sailing with guests I keep it on "vibrate" so they don't hear it, but it reminds me to check our blind spot every few minutes -- helpful in crowded Western LIS on a weekend day sail.

http://www.sagemeditation.com/products/gong-timers-zen-clocks/invisible-clock-ii.html

The only negative is the battery life is only so-so, but it might be better if you don't use vibrate.