First, if you're going to get it, get it cheaper than at the Sharper Image. I found it here for $114.99:
Anyway, from what I'm gathering, it's not simply that you put the watch on and you get a continuous read- you need to press two fingers on the metal buttons on the face of the watch and hold it there while exercising to get your current heart rate. This can cause you to slow down, which could result in a lower heart rate number registering while you're exercising. There's not a really good way of monitoring heart rate with this watch- it would be better if you just hit the buttons at the end of your workout, then continued to take readings to determine how quickly your heart rate dropped.
Any of the other monitors out there that just require you to push and hold a button while working out will do. There are a few- try www.heartmonitors.com
and use the comparison chart to pull up all their strapless monitors.
It seems a bit much just to avoid wearing a strap. For what it's worth, I truly think it's easier and more accurate just to wear a monitor with a strap.
If you get it, give us a review. I've heard they don't last long, which is your caveat.