If you're talking about looking at traffic to your web site from mobile devices, you could make a segment where Mobile Device Type = Mobile Phone (and/or Mobile Device Type = Tablet).
If you're talking about a mobile app or something, you could create a segment where App ID exists, or is a certain app or build.
For language, it depends on how you capture the language. If it's in an eVar, just add Language (eVarxx) = Francais (or whatever language you need) to your segment definition.
