If you want a truly portable solution, the Air Copy is a good one

I have also tested another scanning unit, the Canon image formula P208 scan-tini personal document scanner, which was supposed to be a portable solution

Overall, if you are looking for a portable solution that will work gracefully with your smart phone, this is it

I really wanted to like the ION Air Copy portable scanner as a "pretty damn good" solution for putting retired parents to work digitizing shoeboxes full of family photos... but it seems like it's best suited for receipt and document scanning duties.