Hi. I think you may be best looking outside FMP for this control, looking to something in the operating system or a 3rd part app to either log out the machine or send a log out message to FileMaker.
Part of the reason I suggest this is that I think it is pretty hard for an individual FileMaker client to know if *it* is idle. Running a script to check for idleness is bringing the client into a state of non-idleness. Not trying to be funny, but I think that is an issue.
If you do want to do it within FileMaker, I think you at least have to move away from the idle client to another machine- an agent looking for idlers, if you will.
Still don't think this is the right approach, but the idle time of a client was exposed to the plugin API in FM6 and may still be exposed, though I don't know of any plugins that currently work with it (can someone else chime in on this point?). If it is still exposed, you could set up an agent that would use this to look for idle machines every 30 seconds and then use something like
Troi Activator to run a logout script on those machines. Activator lets you run a script on a client by IP address.
You may be able to get a cron to write out the idle times from the server to text file; then have the agent read that as the basis of your Activator calls. Both approaches depend on getting the idle time of your guests from the FileMaker Pro Server. I'm just not sure what the best way to do that would be.