Keyboard/screen activity

Our users are connected to a company Intranet, which, if there is no apparent activity for 2 minutes from a user, forces them to sign in again. This is a nuisance, so is there any way of running something in the background that will show activity to the intranet controls? The users do not want any screens popping up. I have tried a few things but normally end up in a tight loop which uses 40% of CPU. Anyone got any suggestions?