US only - Shopping service PriceAmbush tracks product prices and emails you about significant drops. Search for a product on PriceAmbush—like a Wii, or an iPod—and click the "Add Alert" button to enter your email address and target price. (The significance of your "target price" isn't clear, and of course, a disposable email address is a good idea here, as where to remove alerts isn't obvious either.) Seems like a good service for tracking that purchase that's just a few bucks too 'spensive at the moment. Thanks, Shelly!
AU - looks like a US-only site at this stage, although I couldn't see any information on the site about where the shops are that they track. Certainly the pricing is just done in one (US) dollar amount.