With our REST API you are now able to query complete user reports. Thus, you can access all information which you already know from the co-worker reports in the web-interface, like holiday accounts as well as work time accounts.
Furthermore, you are able to manage absences (holidays, sick days, special leaves and overtime reduction). You can approve, decline, list or edit them, according to your access rights.
You'll find detailed descriptions for the co-worker reports here, and for the absence resource here.