I also wanted my life partner (my lovely wife) to participate. This was going to be the hard part. Behavior modification. So I built a very simple "tracker".(php/codeigniter/mysql) Date, description, category, spender, cost, that could be accessed anywhere.
I asked my wife to start tracking spending. As we had just bought a new house and 1 1/2 year old. She was extremely resistant to the idea. Six months after using the "tracker" she told me that she didn't plan on doing it more than 2 days before she gave up. However since starting it 3 years ago she and I have increased our "frugalness" and really looked where we should spend money (vacations, artisan food and not items to impress other people… such as fancy cars.)
I think part of the trick is not necessarily import or export or "api"ing data. The trick is doing a manual entry for each transaction. Kind of like a spending journal, food journal or just a journal. There still seems to be power in manually entering a transaction, although it might not be by pen and paper.