I have been using the Google desktop version of Sellers Watch for about 6 months, and I can't say enough good about it. I use it as a sidebar app and it gives me instant information on all of our auctions.
For each auction you can see number of hits, watchers, bids, and high bidder. It can also show a thumbnail image of the item which I find useful. Settings can be adjusted to notify by audio or visual when a bid comes in. I had a little trouble setting up the visual notification, but instructions are in the help file - I didn't look hard enough. An email to the author got a quick reply.
There has been one recurring problem with the auction end times not being reported correctly. It seems to be related to daylight savings time changes, as that's when the problem shows up. I'm not sure if it is a bug or something wrong in my configuration but it's a minor annoyance.
I can't do a very good job of describing all the features - you will just have to try it. It's free so the price shouldn't be a problem It's been a big help to me.