Because these methods are statically declared in your controller, your mobile app will incur no view state overhead from using them.
Inside the remoting call, you would then probably either want to use the ConnectApi namespace classes in Apex, or, if we're talking very simple text posts with no @mentions, you could simply construct the sObject in memory and commit it with a save.
Examples of remoting methods and invoking them from JS in your Visualforce page are found in the Visualforce code developer guide. The Chatter ConnectApi classes are documented in the Apex code developer guide.
Be forewarned that ConnectApi classes follow some slightly different rules with regards to "without sharing" declarations, and have different governor limits than traditional limits on queries and DML.
If Apex is not an option, you could use the AJAX toolkit. This is an older way to get Visualforce to talk to an org, but could work. But it is well documented with lots of examples in the world. But this would only happen in a Professional Edition org where API had been enabled.