I've used http://www.auctionsniper.com/
for a few years with good results.
At first I was leary about giving out my ebay user/pass to them but I haven't had any issues & have been using it for a while.
One nice feature is you can select several similar items & have it snipe them one by one until you win one then stop.
I too get annoyed that people up the price significantly sometimes days before the auction ends. They are only making it cost more for themselves because it gives other bidders the time do ruminate & decide the item is worth a bit more. It also makes it easier for shill bidders to bump up the price.