My wife is something of a magpie - a love of all things shiny - particularly jewellery. She is never that impressed with anything gadgety that i buy and at times i think despairs at my love of gadgetry.
There are only 2 gadgets i have ever bought that she has shown any interest in - the first was a harmony remote. It used to drive her mad that there were remotes all over the place. Indeed i remember the look of complete despair on her face when i upgraded my surround speakers and she discovered that the new subwoofer had a remote of its own
Anyway, i bought a harmony 885 and my wife was almost as pleased with it as i was. When i showed her what it could do she was pretty amazed although over the next few months it just became something that was convenient and tidy!
When i got my iphone she was also quite interested - she never really wanted to use it herself but was always saying things like "does your phone do ....." and almost always the answer was yes!
To my complete amazement she actually said to me the other day - "my phone contract is up soon - do you think i should get an iphone too?"
Over the next few days she asked loads of questions about it and had a play with various apps and has now decided that she definitely wants one.
Now coming back to the magpie thing - having seen this thread i asked her specifically "if i was buying you something for Christmas for about £500 would you prefer an iphone or some...."
That was as far as i got before she completed the sentence - with the word "emeralds"!!
So i guess it depends on the woman.
At the end of the day from what you describe it seems pretty clear that it is not something she would ever buy herself. If it was me i would just buy it for her. She will protest that you shouldn't have spent that money on her etc but i suspect deep down she will be over the moon.
Good luck