I've actually asked or one of those Wii -fit things ...my daughter tried one at her friend's house and she said it was really fun - you can dance, ski, whatever you like to do...I don't really understand the concept but she said, 'Mom - you would love this thing...' so as I didn't have any other ideas - I said, 'Go ahead - get that for me..
I always just ask my parents for a check so that they don't have to pay as much for postage as the present cost to mail it from the US to UK- and then I just hit the sales after christmas for clothes, underwear, socks, whatever I may need.
My son has EXQUISITE taste - he's the only one I trust to pick out jewelry or accessories that I KNOW I'll like - it's uncanny. He's also very good at thinking of individualized sort of gifts that show he knows the person and what s/he'll like. No one else in my family can get it as right as he can, so I just say - take Joseph shopping with you - he'll know what I'll like - and it's weird - because he is such a macho masculine guy but he has never gone wrong on earrings or necklaces, bags, whatever - for his sister and/or I. Even my daughter doesn't get it as right as he does.
I also really like gift certificates to Borders - that way I can pick music, books or stationary...whatever I need or want.
I also really like bubble bath - and my favorite only costs £2.89 at Tesco- so that's cheap and easy - ten bottles of that will last me a month (small bottles- I go through about 2 and a half a week ). Cheap and easy gift right there that'd be VERY much appreciated (even one bottle- stocking stuffer)
Speaking of stocking stuffers - those little cadbury magical elves (chocolate candies) 20 pence a piece.
Really - your wife probably just wants to feel that you know her enough to know what she'd like- that'd be the best present...