We do something similar to this on Lanyrd - try shrinking the browser window on http://sxsw.lanyrd.com/ for example. The labels on the tabs change from "your sessions, your contacts' sessions, all sessions (1114), attendees (2594)" at the widest setting to "you, contacts, all, attendees" on narrower screens.
It's implemented by wrapping a span with a class of "not-narrow-friendly" around the words that should be hidden at narrow widths, then using media queries to hide them.
It's implemented by wrapping a span with a class of "not-narrow-friendly" around the words that should be hidden at narrow widths, then using media queries to hide them.