I think it'd be nice to be able to set up an automated email notification when auctions with certain keywords were up. Ideally being able to specify for them inside a category too (Example: Guppies - koi). I know this is a bit redundant with the "wanted" listings but I think it might be much more efficient, specially since wanted listings are rare.

It'd just be very convenient to receive an email alert when an auction that fulfills the requirements is posted. Perhaps this would even be good to increase bidding by attracting the occasional bidders that are only interested in very specific stuff and don't log in often.

While others' suggestion of searching by countries hasn't been incorporated this would also combine well with that. Perhaps a Category + country + keyword(s) email alert would be the most useful.