The first time I went to China and spoke basically no Mandarin (just "want", "don't want", "this one", "that one", "how much money", "thank you") I took a cheap calculator when I went shopping for electronics and just let people type in the price they wanted. It was also useful for haggling too.
When I went to Thailand all the merchants had calculators for exactly that purpose:)
That, and a small notebook (many people can read a bit of English better than hearing it) can get you 99% of the way there. I did a lot of traveling pre-mobile and pre-internet and these simple tools served me very well!