My wife was against it, so I bought it in secret, let it run around the house during the day, and she was amazed at all the cleaning I was doing. A few months later, I let her into my dark secret, and now she loves it too.
Speaking of wife, I bought her a hooded blanket with an electric warming bag a few years ago. Within 3-5 minutes it's nice and toasty, and she's used it practically every day since I bought it.
Your wife sounds like mine. I value transparency and openness fundamentally, but after a decade of "no" to almost everything, I've learned that if I just do stuff without asking, she frequently says, "Oh, that's a nice idea." If I ask, however, it's "not a good idea," "not now," "we don't need that," etc.