How can I make WordPress show different menu entries when my site is accessed from a mobile browser?

WordPress already allows us to create multiple menus and edit their items. I would like to offer one kind of menu (with more items) to my users coming from desktop browsers and a more condensed menu to user-agents which reveal that they are using mobile browsers.

My theme is already using a responsive menu which shrinks it when the screen size is too small, but I'd like to take it one step further, since I have a bit too many options in my main menu to make for comfortable browsing on mobile.

via Chebli Mohamed