You can get the EA or metadata from component from external call using LSCS (REST API) if you are using TS and LS 7. for more details please refer the lscs technical referece document.
To get EAs fom any asset using the runtime, you have to query the LSCS instance (using LSCS client) in an external. You can get the current page from RequestContext, then do query for that object and parse the XML data.
'LiveSite Content Services 7.x Technical Reference Guide' should have it.