Web based remote access

I want a web based Remote access system through which user can access any other computing device through [login to view URL] perform anything on that device. see the existing web based system logmein ,webexmeeting,Anyplace Control.e.t.c. Major functions:-screen sharing,control mouse and keyboard and file sharing [login to view URL] i want to specify some boundries of [login to view URL] i dont have much time for this software. Boundaries of System:- i want ony screen sharing,mouse and keyboard control and file sharing [login to view URL] need of VOIP,chat client or anyother extra [login to view URL] is sufficient that one client can access one device at a [login to view URL] need of access more than one device on one account at same time.