user monitoring

[Redook]

Hello,

I need to write an application that would monitor which X applications 
are used and what user is doing (if he's using mouse/keyboard with apps).
My first idea was to monitor X events, I created a client that would 
subscribe to events for all windows and somehow identify currently used 
windows by Focus events. Unfortunately there's a problem with 
identyfying the process that window belongs to (I used_NET_WM_PID 
property but not every window has it). There's also probloem with 
getting some events (i.e. button press) that I'm also interested in.

Now the question - is there any way to identify application having 
widowid or other way to achieve what I'm trying to create? Maybe 
modifying X source could give some better results, although I'd like to 
stay away from that if possible.

Thanks,
Michal